Economic zoo

UNIT-1

BENEFICIAL AND HARMFUL INSECTS

At the Garden Line, we receive numerous calls from homeowners who want to spray their plants because there is a BUG on them. Before suggesting a pesticide, I always ask the homeowner to describe the insect, because not all insects are harmful. The overly protective homeowner spraying any and all insects may actually be contributing to a build-up of harmful insects. Ladybugs, for example, eat aphids. Destroying the ladybugs will allow the aphid population to increase.

Positive identification of insects is important. Equally important is the identification of the insect at its different life stages. For example, most people are familiar with the adult form of the ladybug, but few recognize this beneficial insect in its larval form. Unfortunately, the larvae looks nothing like the adult and are often sprayed by homeowners who assume they are harmful insects.

What follow is a list and description of some of the most common beneficial insects. Homeowners should take care not to kill any of these insects. If the population of these beneficial insects is high, there is a high population of harmful insects to feed on; with no harmful insects to feed on, the beneficial insects will leave.

DRAGON FLY-Both the adult and nymph form of this insect are active predators on many insects, but are especially predacious on mosquitoes. The dragon fly spends much of its life cycle around or in water, which are also the breeding grounds for mosquitoes. Many type of dragon flies are common to this area. Adult size may range from 3.8 - 7.6 cm. in length, and colour ranges from brown to blue.

LADYBUG-Also called the "lady bird," this insect is more correctly called a "lady beetle." Many different types of lady beetles are found in North America, and almost all are considered extremely valuable predatory insects. As a whole they prey mainly on soft-bodied insects such as aphids, mealy bugs and scale insect, but they also feed on egg masses of many other insects. The soft-bodied, unattractive, black-and-orange spotted larvae of this insect do not resemble the attractive hard-bodied-orange and black spotted parents, but the larvae are ferocious insects with an insatiable appetite for aphids.

GROUND BEETLE-A very large family of insects with over 2500 species in North America. These hard-shelled beetles are mostly black in color but can have an iridescent hue to their shell. They are mostly night feeding insects and not commonly seen during the day, unless found hiding under stones or debris on the soil. As a family they are considered highly beneficial, with both larvae and adult forms feeding on numerous insects, slugs and snails. They are also reported to consume soil maggots, cutworms and other soil borne larvae. Adult ground beetles are approximately 1 cm. in length.

GREEN LACEWING-These beautiful and delicate insects have earned a common name of "aphid lions," because of their enormous appetite for aphids. Both adult and larvae forms also feed on mealy bugs, other small larvae and eggs of many insects and mites. The brown lacewing is more common in the USA, where it is often called the "aphid wolf." Green lacewings are easily recognized by their large, delicate and usually transparent wings, with green and black venation. The fierce-looking mouth parts of the lacewing larvae help to reinforce its common name of aphid lion. Adult lacewings are approximately 1-2 cm. long.

BLISTER BEETLE-This insect can be both beneficial and harmful. The adult form of the Nuttall blister beetle will consume foliage and flowers of plants in the legume family, and therefore can be quite destructive. However, the larvae form of this same insect will also consume large volumes of grasshopper egg masses. The blister beetle is easily recognized by its dark, metallic green or purple shell, giving it an iridescent sheen. These insects are seldom noticed except when the adults swarm in June. The adult form is approximately 2 cm. in length. If blister beetles are found feeding on desirable plants (caragana, honeysuckle, beans, peas), spray the plants with water to discourage the insects. If this fails, resort to a pesticide to protect the plants.

AMBROSIA BEETLE: Xyloborus dispar (Fabricius)

Life Cycle: Overwinter as adults in host. Adults appear in April and after mating, tunnel into a host to lay eggs. Larvae are present May-July. New adults remain in host to overwinter. One generation per year.

Monitoring: Tanglefoot or some other sticky material applied to the trunks may trap adults and indicate their presence. Ethanol-baited Lindgren Funnel Traps can also be used to detect adults. Look for small exit or entry holes (2mm).

Hosts: Native and cultivated trees.

Comments: Ambrosia beetles tunnel into heartwood causing brown strips of dead tissue in the cambium and discoloration in the heartwood. This contrasts to shothole borers that feed on the cambium, leaving a network of tunnels under the bark.

Body length: Adult - 3.0mm; Mature larva - 4.0mm

Apple Curculio Anthonomus quadrigibbus (Say)

Life Cycle: Overwinter as adults under the host; eggs are laid May to late June. Larvae are present June to mid-July. New adult generation active mid-July to mid-August before overwintering. One generation per year.

Monitoring: No monitoring plan developed. Limb taps around petal fall of pear are useful to detect adults. Inspect young fruit for feeding and/or egg-laying punctures.

Hosts: Apple, pear, crabapple, hawthorn, quince, cherry.

Comments: The reddish-brown adult weevils are slow-moving and will drop readily and play dead when disturbed. They could be mistaken for a piece of debris on a beating board until they resume activity.

Body length: Adult - 5.0mm; Mature larva - 6.0mm

SHOTHOLE BORER Scolytus rugulosus (Ratzeburg)

Life Cycle: Overwinter as mature larvae or pupae in host. Adults emerge in May and tunnel under bark to lay eggs. Larvae present April-July; second adult generation appears August-September to produce overwintering larval generation. Two generations per year.

Monitoring: Glass barriers with a base filled with soapy water can be suspended in orchards to monitor adults. Check branches for entry holes near buds.

Hosts: Native and cultivated trees.

Comments: The presence of small holes at the base of buds and sometimes strings of clear gum or resin exuding from entry holes is characteristic of shothole borer attacks. Larvae feeding on the cambium will create a network of tunnels under the bark. This contrasts to ambrosia beetles that tunnel into the heartwood and cause some discoloration of the cambium and heartwood.

Apple Aphid Aphis pomi (DeGeer)

Life Cycle: Overwinter on host as black eggs that hatch near bud burst. Several generations are produced on host trees during the summer (females only). Winged males and females appear in late summer to mate and lay overwintering eggs.

Monitoring: Beginning late May to early June, examine shoot leaves for presence of aphids and beneficial insects. Young, non-bearing trees should also be inspected.

Hosts: Apple, pear, hawthorn, quince, pyracantha.

Comments: The spirea aphid (Aphis spireacola), identical to the apple aphid in appearance and life cycle, is becoming more common in many orchards. The spirea and apple aphid are bright green with black legs; the apple grain aphid is pale green with a darker green stripe and tan legs. The three aphids can appear together early in the season. The eggs of all species are oblong and shiny black in colour.

Body length: Adult - 2.0mm; Mature nymph - 1.8mm

INSECT VECTORS OF HUMAN DISEASES

In epidemiology, a vector is an insect or any living carrier that transmits an infectious agent. Vectors are vehicles by which infections are transmitted from one host to another. Most commonly known vectors consist of arthropods, domestic animals, or mammals that assist in transmitting parasitic organisms to humans or other mammals. A vector is not only required for part of the parasite's developmental cycle, but it also transmits the parasite directly to subsequent hosts.

Humans have died over the years because of diseases carried by insects. The number is not small either as millions have perished from these diseases over time. Man struggles to overcome these diseases but it is a long, expensive and hard fight especially in areas of extreme poverty. Some insects infect man directly and some indirectly. Animals infested with insects are among the worse as humans ingest food from these animals and are infected with disease.

Arthropods as vector

Arthropods form a major group of disease vectors with mosquitoes, flies, sand flies, lice, fleas, ticks, mites and cyclops transmitting a huge number of diseases. Many such vectors are haematophagous, meaning they feed on blood at some or all stages of their lives. When the insects blood feed, the parasite enters the blood stream of the host. This can happen in different ways. The Anopheles mosquito, a vector for Malaria, Filariasis and various arthropod-borne-viruses (arboviruses), inserts its delicate mouthpart under the skin and feeds on its host's blood. The parasites the mosquito carries are usually located in its salivary glands (used by mosquitoes to anaesthetise the host). Therefore, the parasites are transmitted directly into the host's blood stream. Pool feeders such as the sand fly and black fly, vectors for Leishmaniasis and Onchocerciasis respectively, will chew a well in the host's skin, forming a small pool of blood from which they feed. Leishmania parasites then infect the host through the saliva of the sand fly. Onchocerca force their own way out of the insect's head into the pool of blood. Triatomine bugs are responsible for the transmission of a trypanosome, Trypanosoma cruzi, which causes Chagas ‘disease. The Triatomine bugs defecate during feeding and the excrement contains the parasites which are accidentally smeared into the open wound by the host responding to pain and irritation from the bite.

There are many ways that insects can transmit disease even without transferring germs. There are various mites and worms that will invade tissues. Allergies can flare from bites of bees, body lice, and bites of chiggers and ticks. Some flies will be called mechanical carries as they pick up germs by biting a diseased animal and then bite a healthy person thus contaminating them with disease. There are germs on garbage and other filth that a fly can crawl on it or walk on it and carry disease to humans. Fleas carry disease after ingest plague organisms.

Examples of vectors

• Fleas, typically human fleas such as Pulex and Xenopsylla transmit bubonic plague.
• Mosquitoes of the Anopheles genus transmit human malaria
• Aedes mosquitoes are vectors of avian malaria, dengue fever, yellow fever and chikungunya
• Several genera of Tsetse flies are vectors of human African trypanosomiasis also known as "African sleeping sickness"
• Triatomine bugs are vectors of Chagas disease
• Ticks of the genus Ixodes are vectors of Lyme disease and babesiosis
• Phlebotomine sand flies transmit leishmaniasis, bartonellosis, sandfly fever and pappataci fever.
• Numerous species of ticks and lice transmit various members of the bacterial genus Rickettsia
• The crustacean Cyclops transmits the nematode Dracunculus medinensis.
• The Glassy-winged sharpshooter transmits the Xylella fastidiosa bacterium among plants, resulting in diseases of grapes, almonds, and many other cultivated plants.

·         Mosquitoes are of the insect order Diptera and this group of insects can cause more destruction in terms of human deaths and illness. Mosquitoes are all over this earth except in the Polar Regions. They are carriers of malayan filariasis, bancroftian, dengue, yellow fever and malaria and some kinds of encephalitis. The species of mosquitoes that carry human malaria are the dapple-winged Anopheles. The cells The greatest outbreaks of malaria are in the temperate regions and the Tropics. Anywhere there exists a mild climate and abundant water.

Mosquitoes will bread and multiply.   

People tend to spend more time outside in these areas. Screened porches and houses do not necessarily keep out these mosquitoes. In the United States there are at least a dozen species of Anopheles mosquitoes. There are many species of the Anopheles that exist in other parts of the world. Some carry malaria and others do not. The mosquito known as the yellow-fever mosquito is a semi domestic. Yellow fever is still a serious threat in many places in the world. An infected monkey or even man can spread this virus. It can be found breeding in water and various places such as old tires, vases or cans. The female is the one that bites.

·         A breed of mosquito called Culex tarsalis and several other species of mosquitoes are transmitters of Encephalitis. This is one of several kinds of viruses that attack the central nervous systems of vertebrates. In the Tropics and subtropics Elephantiasis a disfiguring malady of humans is caused by mosquitoes.

Aedes aegypti

The yellow fever mosquito, Aedes aegypti (=Stegomyia aegypti, =Aedes (Stegomyia) aegypti), is a mosquito that can spread the dengue fever, Chikungunya and yellow fever viruses, and other diseases. The mosquito can be recognized by white markings on legs and a marking in the form of a lyre on the thorax. The mosquito originated in Africa but is now found in tropical and subtropical regions throughout the world.

Spread of disease and prevention

Aedes aegypti is a vector for transmitting yellow fever. Understanding how the mosquito detects its host is a crucial step in the spread of the disease. Aedes aegypti are attracted to chemical compounds that are emitted by mammals. These compounds include ammonia, carbon dioxide, lactic acid, and octenol. Scientists at the Agricultural Research Service have studied the specific chemical structure of ocentol in order to better understand why this chemical attracts the mosquito to its host.^[3] They found that the mosquito has a preference for “right-handed” octenol molecules. The term “right-handed” refers to the specific orientation of the molecule, which can either be “right-handed” or “left –handed.” This discovery helps scientists understand how the mosquito seeks out its host and may enable them to develop more effective forms of mosquito repellant.

Culex quinquefasciatus

Culex quinquefasciatus (earlier known as Culex fatigans) is the vector of lymphatic filariasis caused by the nematode Wuchereria bancrofti in the tropics and sub tropics.

Primary vector of Filariasis in India

This is the primary vector of fiariasis in India.It is a strong winged domestic species seen all over India in and around human dwellings. Rapid urbanization and industrialization without adequate drainage facilities are responsible for its increased dispersal. The species is highly anthropophlic (they prefer human blood). They enters the houses at dusk and reaches maximum density by midnight. The peak biting time is at midnight. Legs, particularly below the knee are the preferred biting sites. During day, it may be seen resting indoorson walls, underneath furniture, hanging cloths and in dark corners.

IXODES SCAPULARIS

Ixodes scapularis is commonly known as the deer tick or blacklegged tick (although some people reserve the latter term for Ixodes pacificus, which is found on the West Coast of the USA), and in some parts of the USA as the bear tick,^[1]. It is a hard-bodied tick (family Ixodidae) of the eastern and northern Midwestern United States. It is a vector for several diseases of animals and humans (Lyme disease, Babesiosis, anaplasmosis, etc) and is known as the deer tick due to its habit of parasitizing the white-tailed deer.

PEDICULUS HUMANUS

Sucking lice (Anoplura) have around 500 species and represent the smaller of the two traditional suborders of lice. The Anoplura are all blood-feeding ectoparasites of mammals. They can cause localised skin irritations and are vectors of several blood-borne diseases. Children appear particularly susceptible to attracting lice, possibly due to their fine hair. At least three species of Anoplura are parasites of humans; the human condition of being infested with sucking lice is called pediculosis. Pediculus humanus is divided into two subspecies, Pediculus humanus humanus, or the body louse, sometimes nicknamed "the seam squirrel" for its habit of laying of eggs in the seams of clothing, and Pediculus humanus capitis, or the head louse. Phthirus pubis (the crab louse) is the cause of the condition known as crabs.

Sand flies are blood suckers and carry at least a few serious diseases. In some South American countries the veruga or Oroya fever is carried by sand flies, or as the 8-Day fever of the regions of China, India, Iraq, or the Mediterranean region. This is a mild febrile disease. There is a skin disorder called Oriental sore that is carried by sand flies. Where there are crevices in rocks and walls and damp animal and vegetable wastes the flies will breed. Moth flies breed in sewage and carry disease. Black flies of the family Simuliidae are small humpbacked gnats exist in the United States and in many other countries. Humans can be severely allergic to them or have severe dermatitis. These flies are hosts for early stages of roundworm that can cause onchoceriasis by getting in the eyes and even have caused blindness in some cases. Horse and deer flies are aggressive bloodsuckers who prefer livestock but will bite humans with painful bites. These flies carry tularemia on their beaks. Tsetse flies carry African sleeping sickness. These dangerous flies are in tropical and subtropical Africa and much is done to stop their

Development

House flies will live in the human home and lay eggs and have a new generation within two weeks. They will breed in fermenting vegetable and animal matter. They are known to have spread tuberculosis, parasitic worms, yaws, trachome and cholera. Blow flies are known as the blue bottle or the green bottle flies and carries much of the same disease-producing organisms as the house fly. There is a fly in the tropical Americas called the Dermatobia. It will infest man causing maggots to pop out of the eggs and burrow in the skin.

A breed of mosquito called Culex tarsalis and several other species of mosquitoes are transmitters of Encephalitis. This is one of several kinds of viruses that attack the central nervous systems of vertebrates. In the Tropics and subtropics Elephantiasis a disfiguring malady of humans is caused by mosquitoes.

Fleas have parasitic habits in the adult stage only. They are able to move rapidly among hairs or feathers of their hosts with their wingless adult laterally compressed bodies and strong, spiny legs. If a human is bit there will be an immediate area of inflammation. The human flea is called Pulex irritas as it can live in clothing instead of fur. Rat, cat and dog fleas will carry disease from the host to humans. In the Tropics there is a flea called the chigoe that will bury themselves in the skin, especially feet and cause an ulcer like crater. There are species of fleas that carry the bubonic plague and murine typhus to humans living in warm climates. Bubonic plague is the most serious disease that the flea has causes.

Caterpillars need to be mentioned even though they do carry disease as they can cause many painful injuries. The sting of the caterpillar can be very painful. The puss caterpillar can give a severe sting that gives a human the symptoms of paralysis. Ants, wasps and bees will sting man sometimes causing a very allergic reaction requiring medical attention. The brown-tail moth stings and will irritate the skin and eyes of many humans.

The bed bug is of an order of insects called the Hemiptera. This order includes wingless bed bugs, winged, biting, blood sucking, assassin, bugs, conenoses and their relatives. These bugs live in areas of filth in houses, hotels and in public transportation areas. They will retreat to mattresses, joints of wood, cracks, and can fit into very tight crevices. It has not been proved that these bugs are carriers of disease but that they are the causative agents of several diseases such as plague, relapsing fever, infectious jaundice, lymphocytic choriomeningitis and tularemia. They have been known vectors of Rocky Mountain spotted fever. Some of these bugs will attack humans.

There are three kinds of sucking lice that will infest man, the head, body, and crab lice. The crab lice prefer hairy parts of the human body and will cause intense itching. The other lice have caused the disease, "red death" in the middle ages. The body louse can adapt readily to the human host. Louse-born typhus, like plague, has been one of the worst vermin-infestations of humanity. Epidemics have spread because of lice.

Ticks are mites are a class of arthropods of the Acarina. They have four instead of three legs in the nymphal and adult stages and lack a separate thoracic region as true insects have in their bodies. Half of the species of ticks feeds upon man. Scabies is caused by the itch mite. Grocer's itch and harvester's rash are caused by mites that infest grain and stored-food products. There is a tropical rate mite and a house-mouse-infesting mite that causes infestation of houses.

Chiggers belong to the mite family Trombiculidae. Scrub typhus is caused by certain species of chiggers. It is passed from one generation of mites to the next through the eggs. Certain species of chiggers will even attack man.

There are many more insects that will be carriers of human diseases, too numerous to mention.

Scientists are working all the time to find ways to prevent insects from carrying disease to humans. One method is to destroy the insect vector, by using drugs to kill or by immunization making the human host immune to the insect bites.

PESTS OF SUGARCANE

Sugarcane is any of 6 to 37 species (depending on which taxonomic system is used) of tall perennial grasses of the genus Saccharum (family Poaceae, tribe Andropogoneae). Native to warm temperate to tropical regions of Asia, they have stout, jointed, fibrous stalks that are rich in sugar, and measure two to six meters (six to nineteen feet) tall. All sugar cane species interbreed, and the major commercial cultivars are complex hybrids.

Today, sugarcane is grown in over 110 countries. In 2009 an estimated 1,683 million metric tons were produced worldwide which amounts to 22.4% of the total world agricultural production by weight. About 50 percent of production occurs in Brazil and India.

Sugar cane products include table sugar, Falernum, molasses, rum, cachaça (the national spirit of Brazil), and ethanol. The bagasse that remains after sugar cane crushing may be burned to provide heat and electricity. It may also, because of its high cellulose content, serve as raw material for paper, cardboard, and eating utensils that, because they are by-products, may be branded as "environmentally friendly"

Sugarcane is a long duration crop of 10-18 months and therefore is liable to be attacked by a number of insect pests and diseases.  According to an estimate, sugarcane production declines by 20.0 and 19.0 % by insect pests and diseases respectively.  To increase the crop productivity, management of insect-pest and diseases is of great significance.  Due to diversity in agro-ecological conditions the importance of insect pests and disease varies and therefore, management strategy should be adopted accordingly.

Sugarcane is infested by about 288 insects of which nearly two dozen causes heavy losses to the quality as well as quantity of the crop, The scenario of insect pests and diseases varies in sub-tropical and tropical belt of sugarcane.  Top borer and stalk borer are found pre-dominantly in sub-tropical areas whereas internodes borer and early shoot borer and among disease rust & eye spot are prevalent in tropical region

            Several management strategies have been developed as a result of research and development work.  In order to save environment from chemical pollution, use of bio-control has been given utmost attention.  The management technologies have been integrated as per need for increasing the efficiency.

The cane grub can substantially reduce crop yield by eating roots; it can be controlled with Confidor or Lorsban. Other important pests are the larvae of some butterfly/moth species, including the turnip moth, the sugarcane borer (Diatraea saccharalis), the Mexican rice borer (Eoreuma loftini); leaf-cutting ants, termites, spittlebugs (especially Mahanarva fimbriolata and Deois flavopicta), and the beetle Migdolus fryanus. The planthopper insect Eumetopina flavipes acts as a phytoplasma vector, which causes the sugarcane disease ramu stunt.

        EXTENT OF LOSSES DUE TO DIFFERENT INSECT & PESTS IN INDIA

S. No.	Name of Pest	% reduction in cane yield	% reduction in sugar recovery
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.	Early shoot borer Internodes borer Top shoot borer Stalk borer Gurdaspur borer Rood borer Scale insect Mealy bug Black bug Pyrilla Arboridia sp. White Fly White grub(H) Whiter grub(L) Termite Rodents Sugarcane woolly aphid	22 to 33 34.88 21-37 upto 33 5-15 35.00 32.60 poor germination upto 35 31.60 14.70 86.00 80 100 33 22.27 7 to 39	2 CCS 1.7-3.07 0.2-4.1 1.7-3.07 0.1-0.8 0.3-2.90 1.5-2.5 brix loss 16.20 0.1-2.8 2.0-3.0 1.0-1.5 1.4-1.8 5.0-6.0 complete drying 4.5 - 1.2-3.43

PYRILLA PERPUSILLA

Pyrilla perpusilla causes damage to sugarcane through sucking of sap from leaves, leading to reduction of sugar content in plants. Plant height, cropping pattern and rainy season make commercial spraying impractical. Therefore, experiments were conducted on the alternate hosts and native natural enemies of this pest. A coccinellid beetle (Propylea fallax Khuzorian) was observed to feed on Pyrilla eggs. Five species of web-forming spiders (Cyrtophora sp., Plexippus paykulli, Menemerus bivittatus, Tetragnatha sp. and Leucauge sp.) were identified and observed as predators of Pyrilla nymphs. The process of predation by spiders is discussed. Tetrastichus pyrillae (egg parasite) and Epipyrops sp. (nymphal and adult ectoparasite) were quite predominant and found to be effective in reducing populations of Pyrilla perpusilla.

ACHAEA JANATA (Linnaeus)

Hosts

This caterpillar feeds on many different species of plants. Castor bean and croton are preferred hosts. Occasional hosts include banana, cabbage, Chinese cabbage, crown of thorns, Ficus, macadamia, mustard, poinsettia, rose, sugarcane and tomato as well as some legumes, teas, and other Brassica species.

Distribution

This moth is widespread throughout the tropical and subtropical Pacific, in Australia, and the Orient. It was first collected in Hawaii in 1944 and is now present on all major islands.

Damage

Caterpillars feed on leaves of hosts. During population outbreaks, larvae consume most of the foliage leaving just the veins and petioles.

Biology

The entire life cycle from egg to adult takes place in 48-50 days. The population of this moth fluctuates from year to year in abundance and seasonal occurrence.

Eggs

The pale to dark green, hemispherical shaped eggs are 1/25 inch in diameter and have deep striations radiating from a central point giving the egg a sculptured appearance. They are deposited singly or in clusters on either leaf surface. Eggs hatch in 3 to 4 days.

Larvae

Caterpillars have three distinct body regions, the head, 3 thoracic segments and 10 abdominal segments. Each thoracic segment and abdominal segments 5, 6, and 10 bear a pair of legs. Although these caterpillars are the "naked" type, they do have some hairs on their body. There are 6 caterpillar stages, or instars, before pupation. The first stage caterpillars are translucent yellowish-brown in color and about 1/8 inch in length. The next 4 caterpillar stages are variable in color ranging from brownish orange to greyish brown. When fully grown, the caterpillars are about 2-1/2 inches long. Their greyish orange body has a broken black stripe running along the length of each side. There are four white spots on the head of this caterpillar and white spots on the sides of the abdominal legs. A hump located on the back of the caterpillar towards the rear, has two bright red-orange spots. Larvae can be mistaken for that of the guava moth, Anua indiscriminate. They differ mainly in the spotting of the head, sides of the abdominal legs and the color of the "hump". During the last larval stage, also called the "prepupa" by some authors, the caterpillar does not feed and decreases slightly in size.

Each larval stage lasts about 2 days except for the last stage that lasts for about 4 days. The duration of the larval period is influenced by the amount of food available, plentiful food supply lengthens the caterpillar stage.

PUPAE

Pupae are reddish brown, about 1/4 inches in length, and covered by a silken cocoon. Mature larvae build cocoons on or off the plant. When caterpillars drop to the ground before spinning their cocoon, the silken threads become covered with loose particles of soil and litter. Cocoons found under fallen leaves and debris appears as clumps of soil. Caterpillars that remain on the plant to pupate spin their cocoon within a folded leaf. These cocoons have the appearance of a dead, shrunken leaf.

The duration of the pupal stage is influenced by temperature with warmer temperatures shortening the development time.

Adults

The adult moth is 5/8 inch long with a wingspan of 1-1/2 to 2 inches. The forewings are brownish-gray and the hind wings gray with a bright spot of black and white near the tips.

Females start laying eggs 2 to 5 days after emerging from the pupa and lay an average of 1305 eggs during their lifetime. Eggs are laid during the night since the moths are nocturnal.

MANAGEMENT

Non-chemical control

Several parasites of the croton caterpillar are present in Hawaii. The Ichneumonid wasp, Hyposoter exiguae (Vier.) was recovered from larvae and the Tachnid wasps, Blondelia (Eucelatoria) armigera (Coq.) and Chaetogaedia monticola were recovered from larvae and pupae on castor. The egg parasite, Trichogramma minutum, is also present in Hawaii and their eggs were present in all croton caterpillar eggs collected in 1945. Other Trichogramma species have been reported to parasitize 50-83% of croton caterpillar eggs.

An introduction of the egg parasite, Telenomus proditor, into India was successful in providing limited control of croton caterpillars.

Some control has been achieved using entomogenous microorganisms like fungi, bacteria and viruses achieved 80-90% mortality using the fungus, Nomuraea rileyi found the bacterial agent, Bacillus thuringiensis variety kurstaki effective on croton caterpillar. However the B.t. varieties sotto, entomocidus and aizawai were not as effective against later caterpillars stages.

Chemical control

Several chemical insecticides are effective against the croton caterpillar. Pyrethroids insecticides are more effective than natural pyrethrins. Neem seed kernel suspensions are effective feeding deterrents on castor.

RICE

(Sitophilus oryzae).

Sitophilus is a cosmopolitan genus of weevils found on rice, maize and tamarind. It has also been found on Chickpea.

Notable species, the Rice weevil, S. oryzae and the Maize weevil (S. zeamais) both damage a variety of standing crops, and other stored cereals.

Distribution

The two species, Sitophilus oryzae and S. zeamais, are virtually cosmopolitan throughout the warmer parts of the world. In Europe they are replaced by the temperate Palaearctic species S. granarius which is distinguished by the punctate sculpturing on the prothorax and elytra, and by the fact that it is wingless and hence cannot fly.

Life history

Identical to S. zeamais so far as is known, but preferably taking place in rice. Eggs are white and oval. The female lays the eggs inside the grain by chewing a minute hole in which each egg is deposited, followed by the sealing of the hole with a secretion. These eggs hatch into tiny grubs which stay and feed inside the grain and are responsible for most of the damage. Mature larvae are plump, legless and white, about 4 mm long. Pupation takes place inside the grain. The adult beetle emerges by biting a circular hole through outer layers of the grain. They are small brown weevils, virtually indistinguishable from each other, about 3.5-4.0 mm long with rostrum and thorax large and conspicuous. The elytra are uniformly dark brown. Each female is capable of laying 300-400 eggs, and the adults live for five to eight months and are capable fliers. The life-cycle is about five weeks at 30^oC and 70% RH; optimum conditions for development are 27-31^oC and more than 60% RH; below 17^oC development ceases.

Damage

The developing larva lives and feeds inside the grain hollowing it out in the process. In rice (the preferred host) the entire grain is usually destroyed by the time the adult emerges. Pest status: A very serious major (primary) pest of stored rice and other cereals in the warmer parts of the world.

UNIT-2

MOLLUSCS

Molluscs constitute a natural resource of sizable magnitude in many parts of the world. They are an age‐old group represented among the early fossils, a group of great diversity in size, distribution,habitat and utility. The range of their distribution is as extensive in space as in time for it covers terrestrial, marine and freshwater habitats. They include members from the tiny estuarine gastropod Bithynia and small garden snails to the Giant clam Tridacna or the Giant squid Architeuthis.Oysters, mussels, clams, pearl oysters and chank are the important molluscs, exploited in India from time immemorial. Except for chanks, pearl oysters and cephalopod, much attention was not paid for organized exploitation of molluscan resources from Indian waters till recently. Other gastropod and bivalve fisheries are of sustenance nature and are used for edible purpose, source of lime, as decorative shells or for industrial purpose. The molluscs sustain regular and very productive fisheries in our waters. Only a few of the mussels, clams and oysters are now generally eaten and even these are more a poor man’s food.

Methods of Collection

For the quantitative analysis of the mangrove molluscs, hand picking and dredging apart from using the cores in a transect of known area or using a quadrate of known size are some of the techniques used for collection. At the same time the foulers like mussels and oysters are collected by scrapping them using knives, spatula or any other sharp blade like tools from a known unit area either using a quadrate or in terms of numbers collected per man hour. Further the bivalves are generally collected by hand digging and large power dredging methods.In these, the hand digging is traditional, hard and man‐oriented;whereas dredging involves a less man power and money worth but this technique destroys the substrate, where the bivalves live. Therefore, commercially, the hand digging is more preferable technique, without damaging the nearer area (Varshney and Ghosh, 1997).

Tree fauna

Important components of the mangrove fauna are the bivalves (e.g.oysters), barnacles and gastropods that dwell on the prop roots and lower trunks of trees. The density and vertical distribution of these fauna may be estimated by sampling adequate numbers of trees in each station. The trees may be zoned vertically above ground level into 25 cm zones. The number and species of epifauna in each vertical zone are recorded to estimate their density per unit length at different heights.On the seaward edges, encrusting epifauna and gastropods may be up to heights of two meters above the mud surface. Dead stems and trees in the intertidal zone are examined for any borers and foulers.

Preservation of the Sample

Preservation of sample is carried out in three stages namely,narcotization or anaesthetization, killing and fixation and permanent preservation. The process of narcotization ensures that organisms are expanded fully displaying their characteristic features.Menthol Magnesium chloride: The animals are kept in clean water in an enamel tray / Petri dish / bowl depending on the size of the sample. Powdered menthol or magnesium chloride is sprinkled over the

water and covered with a lid. The sample is left undisturbed for at least 12 hours.

Alcohol or Chloral hydrate: 70% Ethyl alcohol or 1 % Chloral hydrate is added drop by drop at frequent intervals to water in which animals are kept and ensuring that the sample is covered with a lid.The next step is fixation. After ensuring that the animals are narcotized they are transferred to containers with fixatives. The common chemical used for fixation of animals in the field is 4 to 10% neutral formalin solution. For molluscs, ethyl alcohol is the best known killing and preserving medium.The animals are finally preserved either in 4% formalin or 90% alcohol or rectified spirit.

Identification Technique

Among the molluscs, the bivalves are selectively rich in and around mangrove environment. The ecosystem provides an ideal niche for the animals due to less water motion, soft substratum and less stress from the predatory organisms, as compared to other environments. Ecological conditions like tidal amplitude, salinity and temperature are favourable for the bivalves to live, feed and multiply. The gastropod molluscs, represented by snails, whelks, limpets, sea‐hares and their allies, are among the commonest epifaunal species that exist in the mangrove ecosystems. The gastropods are suitably adapted to various macrohabitats of the mangrove ecosystems; the pulmonate snails and several other groups have conquered mangrove lands with the elimination of the gills and conversion of the mantle cavity into a lung.The mangroves provide ideal conditions for higher productivity of gastropods, which in turn, serve as food, particularly the veliger larvae, for numerous other animals. Because of their predatory nature, the gastropods occupy a central role in maintaining the functioning and productivity of mangroves through “cleaning” root system from the encrusting fauna like barnacles.

Identification of Bivalves

The bivalves are identified mainly based on the shell morphology. The shell comprises of two valves. If the valves are similar, the shell is said to be equivalve (clams, mussels); if dissimilar, inequivalve (scallops). The outer surface is usually covered with a periostracum. The outer surface may be striated or ribbed. The two valves are held together by an elastic ligament, which leaves a scar on the hinge. The hinge may in addition have interlocking ridges called the dentition. The individual ridges (or teeth) may be similar. The two valves are attracted to the soft body by adductor muscles that produce scar on the interior surface. If each valve has a single such scar, the shell is said to be monomyarian. If there are two scars on each valve, the shell is dimyarian. At hinge, the shell has a projection called the umbo; this always points towards the anterior end of the animal (i.e., the end where the mouth is). Thus we can distinguish an anterior adductor scar and a posterior adductor scar in dimyarian shells. A slender scar often touches these two, that marks the attachment of the mantle edge, is called the pallial line or pallial scar. Some bivalves have the mantle folded into a posterior siphon for conveying water away from the body when the animal is feeding by converted ciliary currents such shells show a pallial sinus in the pallial line.

Identification of Gastropods

The shell characters such as shape, spire length & shape, mouth opening, opercular shape, umbilicus shape and size, colour & ornamentation of the shell are used mainly for the identification of gastropods apart from the internal characters of which the important one is radula.

 Factors Affecting Biodiversity and Conservation

At the moment marine molluscs appear to be least endangered in the same sense as we observe in birds, mammals, reptiles and freshwater molluscs. Commercial exploitation accounts for the greater reduction of molluscan population in nature, pollution and environmental hazards also cause death of molluscs and to a lesser magnitude, the professional shell collection from wild. Indiscriminate fishing from natural bed may lead to depletion of stock of most of the molluscan resources. Very little is known about the destruction of molluscan stock by pollution and collection of ornamental shells by professional collectors from Indian coast.Oyster fishery in India is of sustenance nature and as such there is no possibility of over‐exploitation and depletion in the immediate future, even if fishing is intensified. Suitable farming techniques for increased production are being taken up in several places. Mussel production in India is low compared with many Asian countries and recent studies indicate that fishing efforts can be increased to get more yields from Kanyakumari – Vizhinjam zone for Perna indica and Calicut – Tellichery zone for Perna viridis. It could be seen that during the peak fishing season of mussels, huge numbers of mussel seeds of the size 10 to 20 mm are being exploited from natural bed along with adult and discarded. Instead of discarding the seed, if they are either being reintroduced into the natural environment or utilized for farming will increase the present production of mussels manifold. In recent years, in India, suitable farming techniques are now coming up to promote mussel production.The information on the clam resource potential of India is much limited. The available data from Karnataka and Kerala estuaries indicate that clam resources in these estuaries are by far abundant and there is considerable scope for increased exploitation from many of the estuaries. The mining of subfossil deposits in the estuaries and river beds in Kalanadi and Vembanad lake damages the natural habitat and adversely affect traditional occupation of fishermen (Nayar et al., 1984;Achari, 1988). The disturbance caused by dredging has affected the growth and survival of bivalves such as Paphia malabarica, Meretrix casta and Villorita spp. Identical situation exists in several other Indian estuaries also. In Ashtamudi estuary, where commercial exploitation of short‐neck clam, P. malabarica is done in an area of 15 to 25 ha for the last 15 years witnessed over‐exploitation of undersized clams in recent years leading to depletion of stock. It is felt that commercial leasing out of estuaries or river beds for exploitation of subfossil and live resources should be controlled by seeking advice from expert National Committee on Marine Parks, as there is every possibility of over‐exploitation and fishing of undersized clams from known beds. It is desirable to demarcate

Dredging through detailed geological investigations for exploitation of the subfossil resources. To replenish the stock of live clams “Clam sanctuaries” or “Clam Park” are to be established in known clam fishing estuaries. Clam farming by semi‐culture (transplanting the seed clams from dense beds to other suitable places in the estuary) is suggested to augment production. Natural population of pearl oysters are influenced by numerous factors like recruitment, presence of pests, occurrence of predators like sea stars, sharks, rays and skates, strong current, drifting of sand and unauthorized fishing. Maintaining a “breeding reserve” of pearl oysters in the Gulf of Mannar has been a popular suggestion put forward by earlier workers. The sea ranching of hatchery produced pearl oyster spat to known pearl oyster beds in Tuticorin by Central Marine Fisheries Research institute commenced by 1985 is under constant monitoring. Giant clams are exploited mainly from Lakshadweep and Andaman & Nicobar Islands. All the four species of giant clams from Indian water have been accepted for listing in IUCN Invertebrate Red Data Book (1983). However, the listing under the endangered species would not interfere with mariculture efforts or attempts to improve harvests for local people.The licensing system for fishing chanks by conventional diving exists only in Tamil Nadu and Kerala. The landings of chanks in good quantities are reported recently from Tamil Nadu, Kerala and Karnataka. In few observations along Tamil Nadu coast, presence of undersized juvenile chanks and egg masses in trawl catches were noted and indicated large‐scale destruction of potential stock. It is suggested to regulate trawling operation over the chank beds by observing ‘closed season’ during chank breeding season for conservation of this resource.Existing rules do not permit the divers to collect undersized chanks from the traditional chank beds in Gulf of Mannar and areas in south‐west coast of India. The recent research programmes of Central marine Fisheries Research Institute to augment chank production by rearing and sea‐ranching are quite encouraging measures for conservation of this resource. It is suggested that instead of extensive exploitation ofchanks in Gulf of Mannar, few protected areas may be demarked to serve as perennial breeding reserves. Extensive and indiscriminate fishing by divers of Andaman &Nicobar Islands for Trochus and Turbo causes a decrease in the landings in recent years. The areas around Little Andamans, Nicobar, Katchal and Comorta Islands should be declared as prohibited areas for fishing upto 500 m from shore line, since exploitation appears to be intensive and there is need for management of the resource based on biological nprinciples governing their production and growth. Artificial seed production and sea‐ranching can enhance wild stock position. Juvenile whelks (Babylonia spirata) are exploited in good quantities from east coast of India and at this stage, measures should be taken to avoid over‐exploitation and destruction of the stock. The intensive trawling over the whelk beds in the southwest coast of India may lead to large‐scale destruction of egg mass and exploitation of juvenile Babylonia spp. Regulation to avoid trawling over the whelk bed and a mesh size regulation to prevent exploitation of undersized whelk are to be implemented to conserve this resource. Further hatchery production and sea‐ranching of the seeds can help in increasing the natural stock.

SERICULTURE

Origins of silk

The silk industry originated 45 centuries ago using wild silkworms in North China along the banks of the Huang Ho River. In 195 AD sericulture was introduced to orea and other places. But Indian scholars point to ancient Sanskrit literature that refers to silk as chinon shuka. This appears to show that silkworms were domesticated independently in the foothills of the Himalaya.

Importance of sericulture in developing countries:

The art of silk production is called sericulture that comprises cultivation of mulberry, silkworm rearing and post cocoon activities leading to production of silk yarn. Sericulture provides gainful employment, economic development and improvement in the quality of life to the people in rural area and therefore it plays an important role in anti poverty programme and prevents migration of rural people to urban area in search of employment. Hence several developing nations like China, India, Brazil, Thailand, Vietnam, Indonesia, Egypt, Iran, Sri Lanka, Philippines, Bangladesh, Nepal, Myanmar, Turkey, Papua New Guinea, Mexico, Uzbekistan and some of the African and Latin American countries have taken up sericulture to provide employment to the people in rural area.

Multipurpose use of sericulture

Apart from silk, there are several other bye-products from sericulture. The mulberry fruits are rich in minerals and vitamins and from the roots, barks and mulberry leaves several ayurvedic and herbal medicines are prepared. Some of the woody mulberry trees provide timber which are resistant to termites and the timber is used for making sports items, toys etc. The mulberry branches after silkworm feeding are generally dried and used as fuel particularly in the villages. The foliage of mulberry is used as a fodder for cattle. The mulberry trees are also planted in the embarkment area for protection of the soil to prevent soil erosion, and mulberry trees are planted as avenue trees. The silkworm pupae are rich in oil content and pupal oil is used in cosmetic industry and the remaining pupal cake is a rich source of protein suitable for poultry and fisheries. In some tribal population, the people eat eri pupa as a source of protein and nourishment. The silkworm litter is used for bio-gas production and used as a fuel for cooking in the rural area. Thus sericulture not only provides silk for fashionable clothings, it also provides several very useful bye products to the human society. Therefore, sericulture development provides opportunities to improve the living standards of people in the rural area in developing countries.

SILKWORM REARING AND SPINNING

Introduction:-

Silk is a proteinous filament secreted by a Sericigeneous insect; it is a product of a unique plant and animal interface. Historical evidence shows that silk was discovered for about 3000 years before the industry spread to other parts of the world.

Despite of the onslaught of manmade fibers, silk still reign as the “Queen of Fibers” due to its unique properties.

• Sericulture is a labour intensive agro-based industry normally practiced by farmers in the rural areas.
• In modern terminology sericulture is defined as an activity with rural base and global reach.
• Sericulture is a chain of many inter-dependent farm and non-farm activities, where cultivation of host plant, silkworm seed production, silkworm rearing and cocoon production are farm activities. Silk spinning/reeling, twisting, weaving, printing, dyeing, finishing and marketing are non-farm activities.
• Sericulture activities involve low capital investment and high production returns.
• Short gestation period.
• Creates maximum employment generation opportunities.
• Family labour can be utilized effectively.
• Women folk, old aged and even handicapped can carry-out light nature activities.
• Nagaland is empowered with numerous flora and fauna which includes varieties of sericigeneous insects and their food plant. The soil and climatic condition is favourable for commercial exploitation of Mulberry, eri, muga and tasar (oak tasar).

Silk worm – TYPES

There are five major types of silk of commercial importance, obtained from different species of silkworms which in turn feed on a number of food plants: Except mulberry, other varieties of silks are generally termed as non-mulberry silks. India has the unique distinction of producing all these commercial varieties of silk.

Mulberry:

·         The bulk of the commercial silk produced in the world comes from this variety and often silk generally refers to mulberry silk. Mulberry silk comes from the silkworm, Bombyx mori L. which solely feeds on the leaves of mulberry plant. These silkworms are completely domesticated and reared indoors. In India, the major mulberry silk producing states are Karnataka, Andhra Pradesh, West Bengal, Tamil Nadu and Jammu & Kashmir which together accounts for 92 % of country's total mulberry raw silk production.

Tasar:

·         Tasar (Tussah) is copperish colour, coarse silk mainly used for furnishings and interiors. It is less lustrous than mulberry silk, but has its own feel and appeal. Tasar silk is generated by the silkworm, Antheraea mylitta which mainly thrive on the food plants Asan and Arjun. The rearings are conducted in nature on the trees in the open. In India, tasar silk is mainly produced in the states of Jharkhand, Chattisgarh and Orissa, besides Maharashtra, West Bengal and Andhra Pradesh. Tasar culture is the main stay for many a tribal community in India.

Oak Tasar:

·         It is a finer variety of tasar generated by the silkworm, Antheraea proyeli J. in India which feed on natural food plants of oak, found in abundance in the sub-Himalayan belt of India covering the states of Manipur, Himachal Pradesh, Uttar Pradesh, Assam, Meghalaya and Jammu & Kashmir. China is the major producer of oak tasar in the world and this comes from another silkworm which is known as Antheraea pernyi.

Eri:

·         Also known as Endi or Errandi, Eri is a multivoltine silk spun from open-ended cocoons, unlike other varieties of silk. Eri silk is the product of the domesticated silkworm, Philosamia ricini that feeds mainly on castor leaves. Ericulture is a household activity practiced mainly for protein rich pupae, a delicacy for the tribal. Resultantly, the eri cocoons are open-mouthed and are spun. The silk is used indigenously for preparation of chaddars (wraps) for own use by these tribals. In India, this culture is practiced mainly in the north-eastern states and Assam. It is also found in Bihar, West Bengal and Orissa.

Muga:

·         This golden yellow colour silk is prerogative  of India and the pride of Assam state. It is obtained from semi-domesticated multivoltine silkworm, Antheraea assamensis. These silkworms feed on the aromatic leaves of Som and Soalu plants and are reared on trees similar to that of tasar. Muga culture is specific to the state of Assam and an integral part of the tradition and culture of that state. The muga silk, an high value product is used in products like sarees, mekhalas, chaddars, etc.

Plantation:

• Mulberry is a hardy and fast growing plant and is grown under irrigated as well as rainfed condition. Mulberry can be cultivated as bush or tree type plantation. Mulberry can be grown in almost all types of soil ranging from red loam, alluvial and laterite soil.
• It can be conveniently grown in areas with slightly acidic and alkaline soil through soil corrective measures.
• Castor is fast growing crop and first leaf harvest can be obtained after 3 months of plantation. Kesseru is grown as perennial plants and leaves can be harvested after 2 years of plantation.
• Som and soalu plants are grown as perennial and rearing can be conducted after five years of plantation.
• Oak plants are grown as perennial plants and rearing can be conducted after five years of plantation.

Mulberry silkworms

Silk-that beautiful, light cloth made into the most expensive saris-has humble origins. It is produced by insects called silkworms as a vital part of their growth. Silkworms are the larvae or caterpillars of silk moths. When the time comes for the larva to change into its next growth stage, a pupa, it secretes a long thread of sticky silk. It forms this into a cocoon around itself. Inside the protective cocoon, the larva gradually metamorphoses. After 8-12 days, a moth emerges. Silkworms are fed a diet of mulberry leaves grown especially for this purpose. The practice of raising silkworms is called "sericulture". This industry has led to the diversification of silkworm races and of the mulberry trees used to feed them. It has not so far led to major negative impacts on the wild races of either the silkworms or trees.

Industrious insects :

Many insects are useful to humans, but only two are reared on a large scale: silkworms and honeybees.

Life cycle of the silkworm

Ten species of butterflies produce silk, but only five spin silk that can be wound onto a reel: the Mulberry silkworm, Eri, Muga, Tasar and Anaphe. By far the most important is the Mulberry silkworm, which produces 92% of the world's silk output. This silkworm is the only species widely reared for commercial use. It has been domesticated for so long that it can no longer survive in the wild.

The silk from silkworms is used for making cloth because of its beauty, strength, softness and durability.

Silkworms

The Western Ghats has a wide range of silkworm races. The most commonly used is Pure Mysore, or PM for short. This race is hardy and resists diseases.

Silkworm races differ in certain important characteristics of interest to sericulturists:

Voltinism: The number of generations completed by an organism in a year is known as "voltinism". Univoltines complete one life cycle (from egg to adult to egg) in one year. Bivoltines complete two such cycles, and multivoltines (or polyvoltines) complete more than two. In the Western Ghats region, people use bivoltine silkworms such as Kalimpong-A (also known simply as KA), as well as multivoltines (such as Pure Mysore).

Moultinism: This is the number of times the larva moults during its lifetime. Different races of silkworms moult as many as six times or just twice. In the Western Ghats, only those that moult four times are used because they are most economical.

 Place of origin: Silkworm races are classified as Japanese, Chinese, European and Southeast Asian. Western Ghat sericulturists make use of all except the European races because these require colder temperatures.

Cocoon shape: Different silkworms spin cocoons of different shapes. Silkworms spin round, oval, dumbell- and spindle-shaped cocoons. All of these types are raised in the Western Ghats.

Cocoon colour: Different silkworms spin cocoons of various hues: white, green, yellow, golden and flesh. In the Western Ghats, KA, NB7 and NB4D2 races spin white silk; PM spins green cocoons.

Silk

The cocoons of insects and webs of spiders consist of light, but extremely strong threads. A mulberry silk thread is stronger than a steel wire of the same thickness.

The raw silk is spun into threads and woven into very light, fine cloth. Because silk is highly elastic, it can be woven into a wide range of cloth types, including satin, crepe and voile.

The Western Ghats states-Maharashtra, Karnataka, Kerala, part of Tamil Nadu and, of late, Goa-produce more than 60% of India's silk output. Silviculture is also being introduced in new areas, such as Sirsi Siddapur (North Kanara).

Cocoon shapes and silkworm races

Breeding silkworms

Sericulturists face various problems with existing types of silkworms:

Lack of seasonal and regional silkworm races.
Lack of hardy, productive, disease-resistant silkworm races.
Shortage of bivoltine breeds (that produce two generations a year).

More silkworm breeds should be bred to give rearers a choice of the most suitable race for particular situations. Some 34 desirable characteristics have been identified. Breeding is difficult because almost all of these characteristics are controlled by more than one gene. This makes ii impossible to develop a silkworm race with all the good characters. Researchers are trying to breed races that have just one or two of tile desired characters. For instance, CAC and HR14 races are hardy and bivoltine; NCD has superior dumbbell-shaped cocoons; CDS2 is temperature tolerant. It is also necessary to conserve existing local races of silkworms to conserve the biodiversity of this important species.

Mulberry silkworm species

Bombyx mandarina (wild ancestor)*
Bombyx mori (currently used commercially)*
Bombyx textor
Bombyx croesi
Bombyx fortunatus bombyx arracanensis
Bombyx sinensis* (B. meridionalis)
Theophila religiosa
Rondotia menciana

Future demand for silk

The present global silk production is fluctuating around 70, 000 to 90, 000 M.T. and the demand for silk is annually increasing by 5%. With the increase in population and also with the increased demand for fashionable clothing items due to fast changing fashion designs in developed countries, the demand for silk is bound to increase even more. For increasing the silk production we require highly productive mulberry varieties and silkworm races and also silkworm races tolerant to adverse climatic conditions and diseases which can come mainly from the sericultural germplasm resources and also from the wild relatives of Bombyx available in the natural habitats.

Importance of conservation of silkworm genetic resources

During the recent years, biodiversity conservation programmes have drawn the attention of many countries including developing nations, because of the genetic erosion due to indiscriminate use of bio resources and damage to the environment, destruction of forest, human interference in eco-system, upsetting the equilibrium of the biosphere. The Convention on Biological Diversity (CBD) organised by United Nations Conference on Environment and Development (UNCED) at Rio de Jeneiro Earth Summit in 1992 made an awakening call to draw the global attention for conservation of biodiversity. Since then the biodiversity conservation and gene bank maintenance have gained greater momentum since the germplasm resources are considered as "Common Heritage of Mankind" and "Sovereign Right of Nations". The issues related to access the genetic resources and its sustainable use, benefit sharing, farmers rights are being deliberated at various national and international fora.Realising the importance of biodiversity conservation for sustainable development of agriculture, the Consultative Group on International Agricultural Research (CGIAR) established the International Board for Plant Genetic Resources (IBPGR) in 1974 at Rome with a global network of genetic resources centres, mainly for conservation of natural genetic resources including the wild species to promote crop improvement programmes and increase the food production. The role of wild relatives and wild species in agricultural crop improvement are well known (Rana, 1995). Similarly, there is an urgent need for seribiodiversity conservation, particularly the wild relatives of Bombyx and Bombycidae.

Improvement in silkworm race heavily depended on the geographical races of B. mori and the wild relatives of Bombyx were not explored, unlike in agriculture. Whereas in agricultural, horticultural and sericultural crop improvement programme the wild species of several crop plants have contributed very valuable genes for resistance to diseases and pests and tolerance to adverse agroclimatic conditions (Jackson and Ford-Lloyd, 1990) and similar exploitation of genes from wild relatives of B.mori have not been reported.

The genus Bombyx Hubner (1818) has two species, Bombyx mori L. and Bombyx mandarina Moore. Apart from the genus Bombyx there are eleven other genera in the family Bombycidae Hubner; 1) Genus - Theophila Moore (1867), 2) Genus - Ocinara (Walker 1856), 3) Genus - Mustilia (Walker 1865), 4) Genus - Gunda (Walker 1862), 5) Genus Penicillifera (Walker) 6) Genus - Ernolatia (Moore) 7) Genus - Norasuma Moore 8) Genus - Trilocha Dieri, 9) Genus - Prismosticta (Swinhoe), 10) Genus - Andraca (Walker), and 11) Genus - Ectrocta (Hampson). Among these genera, Theophila and Ocinara are very close to the genus Bombyx. The wild sericigenous species of Bombyx, Theophila and Ocinara are naturally distributed in the Himalayan ranges of Indo-China range and also in Andaman Islands in India, besides, Jawa, Sumatra, Borneo and Malaya Peninsular (Barlow, 1982). The wild species of these genera have not been explored for transferring the useful genes to confer resistance to diseases and tolerance to adverse agro-climatic conditions into the domesticated species, B.mori. The useful genes from the wild relatives of B. mori may be cloned and these cloned genes may be transferred into the germ cells of the silkworm to develop transgeneic silkworm. Hence, there is an urgent need to collect and conserve the wild species of Bombyx, Theophila and Ocinera and study their genetics for possible use in the breeding programme of B.mori and widen the genetic base as well.

Indian gene centre is harbouring great faunal diversity and nearly 11.9% of the world flora are present in India and hence recognised as one among the twelve mega biodiversity rich centres of the world. Floristically India is very rich, harbouring three mega centres of endemnism i.e. Western and Eastern Himalayas and Western Ghats. It is a treasure house of several diverse sericigenous flora and fauna. Wild species of Bombyx and other genera of Bombycidae do exist in the great Himalayan ranges and Andaman islands, under natural habitat and therefore the Indian gene centre possesses a rich seri-genetic resources.

Eggs and cocoons of a wild silkworm belonging to Bombycidae were collected from wild mulberry tree Morus serrata near Kedarnath (30.47 °N, 79.02 °E) at an altitude of 800 meter above MSL (Tikader 2001). The eggs were incubated and rearing was conducted on the mulberry plants at Central Sericultural Germplasm Resources Centre (CSGRC), Hosur and the produced cocoons and eggs are very similar to B. mori. It is a potential and interesting genetic material with several unique characters, utilising such wild relatives of Bombyx, it is quite possible to create additional seribiodiversity and widen the genetic base of B. mori.

Biodiversity is the result of evolution that is a continuous phenomenon induced by natural selection pressure and the population of organisms evolves through adaptation to the biotic and abiotic stress. Ever since B.mori was domesticated, the species does not survive in the wild state in natural condition and also does not survive without human care and hence natural selection induced genetic diversity in B.mori is rather very limited to voltinism. Hence, it is very essential to conserve and utilise the wild relatives of Bombyx mori to broaden its genetic diversity, apart from the geographical races, mutants, sex-limited races, evolved breeds and breeder’s genetic stocks. The wild relatives of Bombyx are very vulnerable and the vulnerability at different spatial and temporal scales are not known. The design of biodiversity network in sericulture involving the complementarity of wild relatives and domesticated B. mori is also not well established. Therefore, conservation of wild as well as domesticated seribiodiversity resources is very essential for sustainable development of sericulture since loss of genetic resources of domesticated and wild relatives of Bombyx species along with their unique genes may disadvantage future generation.

LAC CULTURE

Potential of india in lac production

 Introduction:

Lac is a resinous exudation from the body of female scale insect.Since Vedic period; it has been in use in India. Its earliest reference is found in Atherva Veda. There, the insect is termed as ‘Laksha’, and its habit and behaviour are described. The great Indian epic ‘Mahabharata’ also mentions a ‘Laksha Griha’, an inflammable house of lac, cunningly constructed by ‘Kauravas’ through their enemy ‘Pandavas’ alive.The English word lac synonyms Lakh in Hindi which itself is derivative of Sanskrit word Laksh meaning a lakh or hundred thousand. It would appear that Vedic people knew that the lac is obtained from numerous insects and must also know the biological and commercial aspects of lac industry. It is also worth to mention that a laksh griha would need a lot of lac which could only come from a flourishing lac industry in that period.Since ancient times, Greeks and Romans were familiar with the use of lac. The cultivation of lac insects has a long history in Asia, with some suggestion that it is as old as 4000 years in China where its cultivation accompanied the development of the silk industry.Lac is Nature’s gift to mankind and the only known commercial resin of animal origin. It is the hardened resin secreted by tiny lac insects belonging to a bug family. To produce 1 kg of lac resin, around 300,000 insects lose their life. The lac insects yields resin, lac dye and lac wax.Application of these products has been changing with time. Lac resin, dye etc. still find extensive use in Ayurveda and Siddha systems of medicine.With increasing universal environment awareness, the importance of lac has assumed special relevance in the present age, being an eco-friendly, biodegradable and self-sustaining natural material. Since lac insects are cultured on host trees which are growing primarily in wasteland areas, promotion of lac and its culture can help in eco-system development as well as reasonably high economic returns. It is a source of livelihood of tribal and poor inhabiting forest and sub-forest areas.

Lac insect taxonomy:

The first scientific account of the lac insect was given by J. Kerr in 1782 which was published in Philosophical Transaction of Royal Society of London (vol. 71, pp.374-382). The first scientific name given to it was Tachardia lacca following the name of French Missionary Father ‘Tachardia’. It was later changed to Laccifer lacca Kerr. The other name given to it has been Kerria Lac Kerr.

Phylum - Arthropoda

Class - Insecta

Order - Hemiptera

Suborder - Homoptera

Super family - Coccoidea

Family - Lacciferidae

Genus - Laccifer

Species – lacca

Lac insect belongs to super family Coccoidea which includes all scale insects. Scale insect is a common name for about 2000 insect species found all over the world. Scale insects range from almost microscopic size to more than 2.5 cm. These insects attach themselves in great numbers to plants. The mouth part of these insects is piercing and sucking type. They can be very destructive to tree-stunting or killing twigs and branches by draining the sap.

There are six genera of lac insects, out of which only five secrete lac, and only one, i.e. Laccifer secretes recoverable or commercial lac. The commonest and most widely occurring species of lac insect in India is Laccifer lacca (Kerr) which produces the bulkof commercial lac.Lac insect of South East Asia is referred to as Kerria chinensis.

 Distribution:

Since the lac insects thrive and feed on certain species of the tropical trees, it is found distributed in South-East Asian countries. Lac is currently produced in India, Myanmar, Thailand, Malaya,Lao and Yuan province of China. India and Thailand are main areas in the world, while India has prime position in relation to lac production. Lac cultivation is introduced into Thailand from India.Over 90% of Indian lac produced comes from the states of Bihar, Jharkhand, West Bengal,Madhya Pradesh, Chattisgarh, Eastern Maharashtra and northern Orissa. Some pockets of lac cultivation also exist in Andhra Pradesh, Punjab, Rajasthan, Mysore, Gujarat, and Mirzapur and

Sonebhdra districts of Uttar Pradesh.

Life cycle:

Lac insect is a minute crawling scale insect which inserts its suctorial proboscis into plant tissue,sucks juices, grows and secretes resinous lac from the body. Its own body ultimately gets covered with lac in the so called ‘CELL’. Lac is secreted by insects for protection from predators.Male is red in colour and measures 1.2 - 1.5mm in length. It has reduced eyes and antennae. Thorax bears a pair of hyaline wings. Female is larger than male, measures 4-5 mm in length and has a pyriform body. The head, thorax and abdomen are not clearly distinct. The antennae and legs are in degenerated form, and wings are absent.The Life cycle of lac insect takes about six months and consists of stages: egg, nymph instars, pupa and adult. The lac insects have an ovoviviparous mode of reproduction. Female lays 200-500 ready to hatch eggs, i.e. the embryos are already fully developed in eggs when these are laid. Eggs hatch within a few hours of laying, and a crimson-red first instar nymph called crawlers come out. The crawler measures 0.6 x .25 mm in size. The emergence of nymph is called swarming, and it may continue for 5 weeks. The nymphs crawl about on branches. On reaching soft succulent twigs, the nymphs settle down close together at rate of 200-300 insects per square inch. At this stage, both male and female nymphs live on the sap of the trees. They insert their suctorial proboscis into plant tissue and suck the sap. After a day or so of settling, the nymphs start secreting resin from the glands distributed under the cuticle throughout the body, except mouth parts, breathing spiracles and anus. The resin secreted is semi-solid which hardens on exposure to air into a protective covering. The nymphs molt thrice inside the cells before reaching maturity. The duration of each instar is dependent on several factors, viz.temperature, humidity and host plant.

Nymph and adults of lac insects

After the first moult, both male and female nymphs lose their appendages, eye and become degenerate. While still inside their cells, the nymphs cast off their second and third moult and mature into adult. Both the male and female larvae become sexually mature in about eight weeks. Only the male one undergoes a complete metamorphosis or transformation into another form; it loses its proboscis and develops antennae, legs and a single pair of wings. It is contained in a brood cell somewhat slipper like with a round trap emerges. The adult male is winged and walks over the females to fertilize them. The female brood cell is larger and globular in shape and remains fixed to the twig. The female retains her mouth parts but fails to develop any wings, eyes or appendages. While developing, it really becomes an immobile organism with little resemblance to an insect. Females become little more than egg producing organisms. The female increases in size to accommodate her growing number of eggs. Lac resin is secreted at a faster rate, and a continuous layer coalesces or grows into one body. After fourteen weeks,the female shrinks in size allowing light to pass into the cell and the space for the eggs. About this time, two yellow spots appear at the rear end of the cell. The spots enlarge and become orange coloured. When this happens, the female has oviposit a large number of eggs in the space called ‘Ovisac’. The ovisac appears orange due to crimson fluid called lac dye which resembles cochineal. It indicates that the eggs will hatch in a week time. When the eggs hatch, larvae emerge and the whole process begins all over again after the cycle has been completed and around the time when the next generation begins to emerge, the resin encrusted branches are harvested. They are scraped off, dried and processed for various lac products. A portion of brood lac is retained from the previous crop for the purpose of inoculation to new trees.

Host plants:

Lac insects thrive on twigs of certain plant species, suck the plant sap, and grow all the while secreting lac resin from their bodies. These plants are called host plants. Although lac insect is natural pest on host plant, these insects enjoy the privileged position not being treated as pest. This is because: i) they yield a useful product, ii) the host plants are economically not so important, and iii) the insects cause only temporary and recoverable damage to the host plants. About 113 varieties of host plants are mentioned as lac host plant. Out of which the followings are very common in India:

1. Butea monosperma (Vern. Palas)

2. Zizyphus spp (vern. Ber)

3. Schleichera oleosa (Vern. Kusum)

4. Acacia catechu (Vern. Khair)

5. Acacia arabica (Vern. Babul)

6. Acacia auriculiformis (Vern. Akashmani)

7. Zizyphus xylopyrus (Vern. Khatber- grown in part of M.P. & U.P.)

8. Shorea talura (Vern. Sal grown in mysore)

9. Cajanus cajan (Vern. Pigeon-pea or Arhar)

10. Grewia teliaefolia (Vern. Dhaman preferred in Assam)

11. Albizzia lebbek (Vern. Siris/Gulwang)

12. Flemingia macrophylla (Vern. Bholia)

13. Ficus benghalensis (Vern. Bargad)

14. Ficus religiosa (Vern. Peepal)

Of these host plants, palas, kusum, ber and khair are of major importance, while others are of regional and minor importance. It is also important to mention that the quality of lac is directly related to the host plant and to the strain of lac insects. Based on industrial parameters, kusumi lac is better and fetches higher price in market. In this respect, ber tree asa potential kusumi lac host is already getting momentum. This host species is available in plenty and can supplement and fulfill the kusmi brood lac requirement in many areas.Similarly, siris (Albizzia sp.) has also been identified as good host for kusumi brood lac. The trees can be raised and utilized within a period of 5-6 years of plantation in comparison to around 15 years for kusum. Flemingia semialata is a bushy host plant and has also been identified as well as established as a good kusumi lac host on plantation basis. Thus, these three hosts viz., ber, siris, semialata and lately Prosopis juliflora (in Gujarat areas) are expected to enhance kusumi lac cultivation. Adoption of this activity may enhance lac production to the tune of 3-4%.

Strains of lac insect:

In India, Lac insect is known to have two distinct strains: kusumi and rangeeni. The kusumi strain is grown on kusum or on other host plants using kusumi brood. The rageeni strain thrives on host plants other than kusum. The life cycle of lac insects take about six months,hence, two crops a year can be obtained.In case of kusumi strain, two crops are: i) Jethwi (June / July) and ii) Aghani (Jan. / Feb). In case of rangeeni, tow crops are: i). Karrtiki (Oct. / Nov.) and ii) Baisakhi (May / June). The crops have been named after Hindi months during which these are harvested. The lac of rangeeni crops is harvested while it is still immature. Aghani and baisakhi of rangeeni strain are the main corps contributing about 90% of lac production, remaining 10% is contributed by kusumi crops.However, the kusumi crop lac is considered superior resin, because of the lighter colour of resin,and it fetches better price.

Lac cultivation

Lac cultivation is done by putting brood lac on suitably prepared specific host plants. The brood lac contains gravid females which are about to lay eggs to give birth to young larvae. After emergence from mother cells, the young larvae settle on fresh twigs of host plants, suck the plant sap and grow to form encrustations.

Local practice

 Lac cultivation is simple, does not need any large investment and requires only part-time attention. In India, lac cultivation is carried out casually, and the cultivator is satisfied with what he gets, as it is being regarded as subsidiary crop. The local practices in lac cultivation has some disadvantages like –

 i) The same host plants are continuously exploited without giving rest for recoupment.

ii) Only natural inoculation occurs.

iii) Partial harvest is done leaving few branches untouched for auto inoculation of next crop and no pruning is done.

As a result of the defective local practices, host trees loss the vigour and unable to throw out new succulent shoots, and in course of time, the trees become weak and die. The self inoculation leads to heterogeneous infestation of nymphs, which results in wholesome mortality of brood in seasons of extreme heat, and thereby, the cultivator is forced to abandon lac cultivation.

Improved practice

Sustained production of lac and steady returns can be achieved by adopting improved method of cultivation. The underlying principle in improved method of lac cultivation is to provide much needed rest to the host plants after a harvest has been taken. For this purpose, lac cultivation is adopted. As the term coupe means a chamber, the host plant trees are divided into coupes i.e. groups that consist of certain number of trees. In practice, only few numbers of trees in a coupe are inoculated. Following harvest, these trees are made to rest and recoup the lost vigour, while other trees (which have till now been restring) are ready with succulent twigs for inoculation. Thus, in a coupe system, alternate groups of trees are put to lac cultivation. Full inoculation and full cropping is the rule under this system. In addition, the following considerations are desirable in improved lac cultivation:-

The mean lac productivity (per tree and per unit area) of 2, 5 and 15 kg per tree or 3, 4 and 5 q/ha for palas, ber and kusum respectively in traditional lac culture is very low. This is all due to poor sustainability, continuous exploitation and increased threat from pests. So,the technology of improved scientific method of lac cultivation should be adopted, that includes superior breeds of lac insect, providing proper rest to host plants, use of good quality brood lac in appropriate quantity, post harvest management of lac crop, host plant management and lac pest management.

As the lac cultivation is mainly practiced by the forest and forest fringe dwellers, their involvement in the Joint Forest Management (JFM) programmes in different lac growing states is likelytoenhance the lac production. Lac host trees under the custody of state forest department are out of reach of the forest dwellers and interested lac growers and are not being utilized for lac cultivation. If these are jointly managed by forest department and forest dwellers and they work in close association, it will be a boon for lac cultivation and production.

Timely availability of pest free and quality brood lac is the most important input for lac cultivation. Quality brood lac ensures high fecundity of insects and fewer requirements of inoculums. Timely harvesting of mature crop and proper inoculation will reduce the risk of loss of lac insect to a large extent.

Propagation of Lac Insects

Propagation means the spread of lac insects on the same or different host plants. This is done by inoculation of newly hatched (Brood) nymphs. Inoculation is of two types.

i) Natural or self/auto – inoculation: This type of inoculation occurs naturally. It is very simple and common process, when the swarmed nymphs infect the same host plant again. Natural inoculation, being repeated on the same host, makes in host plant weak, and thereby, nymphs do not get proper nutrition. Also in natural inoculation, it is not sure that uniform sequence of inoculation take place. Therefore, natural inoculation should be discouraged.

ii) Artificial Inoculation: Artificial inoculation is brought about by the agency of man. The main idea behind the artificial inoculation is to check the drawbacks of natural inoculation. In this method, the host plants are first of all pruned in Jan. or June. Pruning means cutting away old, weak and diseased twigs. It induces host plants to throw out new succulent twigs and is as important in lac culture as plouging is for seed sowing in agriculture. Pruning should be done with a sharp instrument (scateur, pruning Shaw and pruning knife) to give a sharp and neat cut. Only light pruning should be carried out.

In artificial inoculation, brood twigs are cut in size 20 - 30 cm in length. Then, the cut pieces of brood twig are tied to fresh tree twigs in such a way that each stick touches the tender branches of trees at several places. The nymphs swarm from brood and migrate to tender and succulent twigs and infest them. Following swarming, the brood twigs should be removed from the host plant, as this would decrease the chance of pest infestation. Following precautions are desirable is artificial inoculation:-

i) Fully mature and healthy brood free from pest infestations should be

taken.

ii) Brood meant for inoculation should not be kept for long and used

immediately after crop cutting.

iii) Tying of the brood lac stick should be done securely on the upper surface of branches. This will prevent falling of twigs and provide full contact for quick and easy crawling of the nymphs. One should keep a watch on the brood lac dropping down.

iv) Some times due to bad weather, swarming of nymphs from brood is prevented. Hence, the room storing brood lac sticks is moderately heated to 20⁰C to induce swarming, and then sticks are tied.

v) Generally, cultivation of kusumi in rangeeni area and vice versa should be avoided.Brood lac from a particular host used year after year is likely to deteriorate in quality. Therefore,alternation of brood and host give production of a better quality of brood lac.

Inoculation period

As discussed above, each strain of lac insects (Kusumi and Rangeeni) yield two crops a year: jethwi and aghani in case of kusumi strain, and kartiki and baisakhi in case of rangeeni. The inoculation period of all the four types of crops is different: for kartiki, June/July; for baisakhi,Oct. /Nov. for agahani, June/July; for jethwi, Jan. /Feb.

Harvesting of lac

Harvesting is the process of collection of ready lac from host trees. It is done by cutting the lac encrusted twigs when is crop is mature. It may be of two types:-

a) In Immature harvesting, lac is collected before swarming, and lac thus obtained is known as ‘ARI LAC’. The immature harvesting has drawbacks, as the lac insects may be damaged at the time of harvesting. However, incase of palas lac (Rangeeni lac), it is found that ARI Lac gives better production. Hence, ARI lac harvesting is recommended in case of palas only.

 b) In mature harvesting, lac is collected after swarming. The lac obtained is known as mature 00Lac. To know the exact date emergence and swarming of nymph, a simple visual method is adopted. A yellow spot develops on the posterior side of lac cell towards crop spread forwards until it covers half of the cell. Cutting of twigs for harvest can be done at any time between the stages while yellow spot occupies one third to one half of the cell area. It is sometimes desirable to wait till the emergence of the first few nymphs. The harvesting periods of different crops are different.

The kartiki crop is harvested in Oct. /Nov.; baisakhi, in May/June;

aghani in Jan/Feb.; and jethwi, in June/July.

When the nymphs have escaped from the brood lac, what is left is the stick lac or phunki lac. These sticks should be tied in bundles and immersed in water, preferably running water for 3-4 days, keeping them well under waters with help of heavy stones. The stick lac should then be kept in shade for drying. The raw lac should be scraped while sticks are still moist.Following consideration are recommended for harvesting:

i) Lac crop should be harvested only when mature. Immature or ARI lac cutting should be avoided, though it is recommended in case of palas.

ii) A mature crop is said to be the one from which nymphs will emerge in 7-10 days. So, the crop should be harvested within the above said days prior to nymphal emergence. If cut earlier, there is a chance of nymphs dying. If cut later, the nymphs may already have emerged before inoculation is adopted.

iii) Attempt should be made to reap the entire crop, if self inoculation is not required. In the case of rangeeni crop, only lac encrusted twigs are cut, while in the case of kusumi one, reaping should combine with pruning.

iv) The brood sticks harvested should be utilized for inoculation as soon as possible. If storage is needed, these have to be stored in a well ventilated room or under shade in open prevented from rain and heat.

v) Harvesting of lac crop at maturity can solve the crisis of brood lac dearth to a large extent without affecting the quality of lac obtained as phunki lac. This will also reduce the loss of brood lac and enhance the yield.

Composition of lac:

The major constituent of lac is the resin. Lac resin is a polyester complex of straight- chain hydroxy fatty acids of C14 – C18 carbon chain (such as Aleuritic acid, butolic acids), mono- and di – hydroxy acids along with hydroxy terpenic acids. Other constituents present are: dye, wax,sugar, proteins, soluble salts, sand, woody matter, insect body debris etc. Lac wax is a mixture of anthroquinoid derivatives. Percent-wise composition of lac given below (adopted from ILRI data): -

Constituent Percentage

Lac resin 68

Lac wax 6

Lac dye 1-2

Others 25

Lac processing:

Stick lac

Following harvest, lac encrustations are removed from the twigs of host plant by scraping.The raw lac thus obtained is known as raw or crude lac or scraped lac or stick lac. This crude lack consists of resin, encrusted insect body, lac dye, sand and twig debris. The freshly scraped lac contains a lot of moisture and usually left to dry. The quality and value of stick lac depend very much upon variety of factors, viz. host tree, climate, whether the crop is harvested before or after emergence of larvae, and the method of drying and storage.The stick lac cannot be stored for longer duration, as the lac has tendency to form lump,and there is loss in quality of lac. High moisture content is responsible for lump formation. The optimum moisture content has been identified to be 4% for storage of stick lac to avoid lump formation. It is recommended to store the stick lac on and racked frequently. If stick lac is converted into seed lac, it can be stored for longer duration like food grains. Establishment of small scale lac processing unit in lac grower villages will help in overcoming this problem.

Seed lac

The primary processing to seed lac soon after harvesting is necessary, because the storage of stick lac is more congenial for lump formation and breeding of storage pests, and thereby causing substantial loses and deterioration in quality of desired industrial parameters. The stick lac is crushed and sieved to remove sand and dust. It is then washed in large vats again and again to break open the encrusted insect bodies, to wash out the lac dye and twig debris. Decaying bug bodies turn the water a deep red that is processed further to get the byproduct lac dye. The remaining resin is dried, winnowed and sieved to get the semi refined commercial variety product called seed lac. The dusty lac eliminated by sieving is refuse lac known as molamma. The seed lac is in form of grain of 10 mesh or smaller and yellow or reddish brown incolour in general appearance. Adhering impurities on the grains of seed lac may be to 3 - 8% (Average 5%).

Following grades of hand made seed lac are commonly available in the market:-

Ordinary/ Genuine bysakhi

Fine bysakhi

Golden bysakhi

Golden kusumi

Golden bysakhi – bold grain

Goden kusumi – bold grain

Golden kusumi seedlac – Medium

Manbhum fine seedlac

(In lac trade, baisakhi crop is commonly referred to as bysakhi or bysacki)

Shellac

The shellac is the name of finished product and is commonly used across the world. Seed lac is processed into shellac by any of the three methods: hand made country Process or heat process or solvent process.

 Hand made Process

Traditionally seed lac is processed by hand. The seed lac is filled into long sausage shaped cloth bag of about 2 inch diameter and 30 feet long. The long bag is passed gradually in front of a charcoal-fired hearth hot enough to melt the lac. By twisting the bag, molten lac is squeezed out through cloth. The residue left inside cloth bag is another variety of refuse lac known as kirilac.The molten filtered mass is stretched into sheets approximately 0.5 cm thick and thinner by skilled work man with the help of glazed ceramic cylinder. Alternatively, the molten mass is allowed to solidify in form of discs, and then it is called as ‘button lac’. The following grades of hand made shellac are commercially available.

Lemon one shellac

Lemon tow shellac

Standard one shellac

Superior shellac

Superior kusumi lemon

Kusumi button lac

superior kusumi button lac

light pure button lac

Pure one button lac

Heat Process

In this process of manufacturing of shellac, the seed lac is melted by steam heat. The molten soft lac is squeezed through filter by means of hydraulic pressure. The filtered molten lac is drawn into long and continuous sheets with help of roller. The sheet is then broken into pieces called flakes. Following grades of machine made shellac are commercially available:

Orange shellac

Lemon one shellac

Lemon two shellac

standard one shellac

Black T.N. shellac

Kusumi lemon shellac

Orange fine shellac

Solvent Processes

If the solvent process is used to purify the semi refined lac, dewaxed and decolorized shellac can be obtained as end product. The normally amber colour resin can also be bleached to get bleached shellac.

Seed lac is dissolved in a refrigerated alcohol and filter through filter press to remove wax and impurities. The colour may be removed to any required standard by charging with the activated carbon and then alcohol is recovered. The molten shellac is stretched with a roller. The solvent process of lac manufacture yields the following grades:

Dewaxed platina

Dewaxed blonde

Dewaxed super blonde

Dewaxed lemon

Dewaxed orange

Dewaxed Garnet

(Actually above nomenclature is based on the colour of and product. For instance, the colour index of platina is about 0.6, of Garnet is 35 and of other varieties fall in between.)In manufacturing bleached shellac, the basic procedure consists of - i) dissolving seed lac in aqueous sodium carbonate solution at 90- 1000 C, ii) stirring off solution with sodium hypochlorite and iii) filtering after cooling. The bleached shellac is reclaimed from the filtered solution with sulphuric acid. The reclaimed bleached shellac is then filtered, washed with water for removal of acid and dried. Bleached lac is white in colour. It has specialized demand and manufactured commercially in two grades:

Dewaxed bleached shellac

Waxy bleached shellac

Aleuritic acid (Shellac aleuritic powder) is also isolated further by saponification from resin lac.

Lac products and their use:

Lac dye

Lac dye is a mixture of anthroquinoid derivatives. It is traditionally used to color wool and silk.

Its colour varies between purple red, brown and orange often depending upon the mordant used.

It is used in food and beverages industry for coloring. In recent past, lac dye has been replaced by synthetic dye. But, now-a-days with increasing stress and awareness on use of eco-friendly and safe material particularly associated with human contact and consumption has made revival of great demand of lac dye as a coloring material.

Lac wax

Lac wax is a mixture of higher alcohols, acids and their esters. It is used in –

Polishes applied on shoes, floor, automobiles etc.

Food and confectionary, and drug tablet finishing

lipsticks

Crayons

Shellac

Shellac is a natural gum resin, a nature’s gift to the mankind and is used in over 100 industries. It is natural, non toxic, physiologically harmless and edible resin. Shellac is a hard, tough, amorphous, and brittle resin containing small amount of wax and a substance responsible for its characteristic pleasant odour. The lac resin is not a single chemical compound, but an intimate mixture of several components. Shellac is slightly heavier than water. Its natural colour varies from dark red to light yellow. When slowly heated, it softens at 65-70oC and melts at 84-90oC.Shellac is insoluble in water, glycerol, hydrocarbon solvents and esters, but dissolves readily in alcohols and organic acids. The solvent most commonly employed to dissolve shellac ismethylated spirit. Usually the milder alkalis, ammonia, borax and sodium carbonate can also be employed to prepare aqueous solutions.

Shellac is acidic in character. Acid value is 70. It is an ester. Saponification value 230. It has free five hydroxyl groups and has hydroxyl number 260. It has unsaturation indicated by iodine value of 18. Free aldehydic group also has been indicated by carboxyl value of 18. Its average molecular weight is 1000. Normal wax content of shellac is 5% which is insoluble in alcohol. It is soluble in n-hexane, pure terpentine, and other hydrocarbon oils. It is hard and point 840 C. It has the following extra ordinary properties:

i) It is thermoplastic.

ii) It is approved for various applications in the food industry.

iii) It is uv-resistant.

iv) It has excellent dielectric properties, dielectric strength, a low dielectric consent, good tracking resistance etc.

v) It has excellent film forming properties. Its film shows excellent adhesion to wide

Variety of surfaces and possess high gloss, hardness and strength

vi) Shellac is a powerful bonding material with low thermal conductivity and a small

Coefficient of expansion. Its thermal plasticity and capacity of absorbing large amounts of fillers is noteworthy.

vii) Shellac under tropical conditions of storage, may soften and form a solid block,

without adverse effects on its properties. Long storage under adverse conditions, however,may lead to deterioration in properties

viii) When shellac is heated for a long time above its melting point, it gradually loses its fluidity and passes through a rubbery stage to hard, horn-like and infusible.

Use:

It is used in fruit coatings, e.g. for citrus fruits and apples, parting and glazing agents for sweets, marzipan, chocolate etc. Also used as binder for foodstuff stamp inks, e.g. for cheese and eggs.

It is used as binder for mascara, nail varnish additive conditioning shampoo, film forming agent for hair spray, micro-encapsulation for perfumes.

It is used for enteric (i.e. digestive juice-resistant) coatings for tablets and as odour barrier for dragées.

It is used in manufacturing of photographic material, lithographic ink and for stiffening felt and hat material.

It is utilized in preparation of gramophone records.

Jewellers and goldsmiths use lac as a filling material in the hollows in ornaments.

It is also used in preparation of toys, buttons, pottery and artificial leather.

It is also used commonly as sealing wax.

With increasing environmental awareness of consumers, this natural and renewable raw material is being used increasingly in the development of new products apart from the conventional user industries. Few to name:

Leather: Seasoning, Leather care products

Printing inks: As binder for flexographic printing inks for non-toxic printing of

food packaging

Wood treatment: Primers, polishes, matt finishes

Textiles: As stiffeners

Electrical: Insulation, capping, lamination

Abrasives: Binder for grinding wheels

Others: Binder for inks and water colours, Micro-encapsulation for dyes

Bleached shellac

Bleached shellac is non-toxic, physiologically harmless (edible), and is widely used in the food industries, food packaging and allied industries. Apart from the above, bleached shellac is also used for its qualities i.e. binding, adhesive, hardening, gloss, odourless, fast drying, and extending shelf life (in absence of refrigeration ) etc. Clear and transparent or very light coloured alcoholic or water - alkali solutions can be obtained from bleached shellac.

Use:

Bleached shellac is widely used in the following industry:

Paints (primer for plastic parts and plastic film)

Aluminium industry (primer for Aluminium and Aluminium foils)

Flexographic printing inks

Pharmaceuticals (for coating of pills, tables and gel caps and coating for controlled release preparation)

Confectionery (in coating of confections, chewing gums, marzipan chocolates, nutties,jelly- and coffee-beans etc)

Binder for food marking and stamping inks and Binder for egg coating

Barrier coating for processed food, vegetables, fruits and dry flowers

Textiles (used as textile auxiliaries and felt hat stiffening agents)

Cosmetics( used in hair spray, hair and lacquers, hair shampoos, and binder for

mascara)

Wood finishing (as binder for wood coatings and wood stains and as filler/sealer for porous surfaces and cracks )

Antique frames for paintings and Wood polish (French polish)

Fire works and pyrotechnics ( as binder for fireworks, matches etc and used in coating of magnesia

Electric (as binder for lamp cements)

Electronics (it is binder for insulation materials, serves as additive to moulding

compounds. Mass coating for print-plates and is adhesive for si-cells.)

Grinding wheels (it is binder for additive of grinding wheels)

Plastic (it is primer for plastic parts and films)

Rubber (it is additive to natural rubber)

Leather (in leather auxiliaries)

Dewaxed bleached shellac

Dewaxed white shellac is used in the same way as any other grade of shellac. The major difference between this shellac and the others is that it is a bit harder, shines a bit brighter, is completely free from wax. Bleached lac has super characteristics and qualities i.e. adhesive, binding, hardening, gloss, odorless. It has good film forming properties, a high gloss and excellent adhesion to various substrates including the human hair. It is non-toxic and physiologically harmless. Good solution can be obtained in ethanol and lower alcohols. It can also be dissolved in water by adding an alkali like Ammonia. It is compatible with many other resins, raw materials and additives used in cosmetics, pharmaceuticals and food formulations.

Use:

Coating of fruits and vegetables

Coating in tablets & capsules

Coating in confectionary

Coating in aluminium foil, paper

Coating in cosmetic industry

In cosmetics, it is used in hair sprays (pump sprays or aerosol sprays, hair setting lotions, hair shampoos, mascara, eyeliners, nail polishes, lipsticks, micro encapsulation by coacervation of fragrances and perfume oils.

In food, it is used for coating of confections, chewing gum, candles, cakes, eggs, citrus fruits and apples, and printing inks for eggs and cheese.

Aleuritic Acid (Shellac Aleuritic Powder)

Aleuritic Acid (9, 10, 16-trihydroxypalmitic acid), obtained from shellac by saponification, is a unique acid containing three hydroxyl groups of which two are of adjacent carbon atoms.Aleuritic Acid is white powder or granule. It is moderately soluble in hot water or lower alcohols (viz. methyl alcohol, ethyl alcohol, and isopropyl alcohol) and crystallizes out on cooling the solution. It is soluble in the lower alcohols such as methyl, ethyl and isopropyl alcohols. Technical grade Aleuritic Acid (purity 99%) a slight yellow and almost odourless solid.

Use:

There is a continuous growing demand of Aleuritic acid in the fields of perfumery and

pharmaceuticals due to it being an excellent starting material for the synthesis of civetone,ambrettolide, isoambrettolide etc, which have the musk like odour. Civetone is obtained from Shellac Aleuritic Acid. It is used for manufacturing of perfumes and is very much in demand with perfume manufacturing companies in France, Italy, Germany, USA etc.The other suggested applications of Aleuritic acid are the following:

Synthesis of Glucose monoaleuritate (a non-toxic non-hemolytic water-soluble compound) in medicine as an isocaloric substitute for dietary tripalmitin.

Preparation of plastics with good adhesive properties by the condensation of Aleuritic acid with pithalic andydride and glycerin, rosin etc.

Aleuritic acid esters used in the preparation of lacquers, plastics and fibres.

Carp polyculture

Carp polyculture in India have been utilizing a huge amount of organic wastes such as cowdung or poultry droppings and production levels of 1-3 tonnes/ha/year can be obtained with application of both organic and inorganic fertilizers alone. Provision of feed enhances the fish production significantly and production levels of 4-8 t/ha/yr are obtained using a judicious combination of both the feed and fertilizers. The packages of practices, as developed at the research institute have been adopted in ponds ranging from 0.04-10.0 ha in area and 1-4 m in depth in different regions of the country, resulting varying rates of production. While small and shallow stagnant ponds have several inherent problems, which adversely affect the growth of fish, the large and deep ponds have their own problems of management. Ponds of 0.4-1.0 ha in size with water depth of 2-3 m are considered to be best for better management. The management practices in carp polyculture involve environmental and biological manipulations, which can be broadly classified as pre-stocking, stocking and post-stocking operations. Pre-stocking Pond Preparations Pond preparation involves making ponds weed and predator-free and generating adequate natural food to ensure high rates of survival and good growth and thereby yields. Control of aquatic weeds, removal of undesirable biota and improvement of soil and water quality are the important aspects connected with this phase of management. The detail regarding the control of predatory and weed fishes have been discussed in nursery management. Stocking of Ponds Ponds are stocked with seed of appropriate size after acclimatizing them to the new habitat when it is ready after fertilization.  Both size and density of fish are important to achieve high yields. Fingerlings of over 100 mm in size are recommended for stocking in grow-out culture ponds. Stocking of smaller size of fishes may result in higher mortalities and slow growth during the initial months. In intensive polyculture ponds, a size of 50-100 g is preferred for stocking to realize higher survival of over 90% and better growth. Generally, a density of 5,000 fingerlings is kept as a standard stocking rate per ha for carp polyculture for a production target of 3-5 t/ha/yr. Stocking densities of 8,000-10,000 fingerlings/ha has been used for production levels of 5-8 t/ha/yr. Higher targeted fish production levels of 10-15 t/ha/yr are achieved by resorting to stocking at a density of 15,000-25,000/ha. In carp polyculture, species ratio are maintained for minimizing the inter-specific and intra-specific competition for food available at various trophic levels and zones in a pond. Two or more species occupying different niches could be utilized in a pond for exploiting the food available at various zones. While a combination of six species viz., catla, silver carp, rohu, grass carp, mrigal and common carp has been proved to be the ideal combination for carp culture in India, species combination largely are decided on seed availability and market demand. Of these catla and silver carp are surface feeders, rohu is a column feeder, grass carp is a macro-vegetation feeder, and mrigal and common carp are bottom feeders. A proportion of 30-40% surface feeders (silver carp and catla), 30-35% mid water feeders  (rohu and grass carp) and 30-40% bottom feeders (common carp and mrigal) is commonly adopted depending on the productivity of the pond. Post-stocking Pond Management Ponds are stocked with seed of appropriate size after acclimatizing them to the new habitat when it is ready after fertilization.  Both size and density of fish are important to achieve high yields. Fingerlings of over 100 mm in size are recommended for stocking in grow-out culture ponds. Stocking of smaller size of fishes may result in higher mortalities and slow growth during the initial months. In intensive polyculture ponds, a size of 50-100 g is preferred for stocking to realize higher survival of over 90% and better growth. Generally, a density of 5,000 fingerlings is kept as a standard stocking rate per ha for carp polyculture for a production target of 3-5 t/ha/yr. Stocking densities of 8,000-10,000 fingerlings/ha has been used for production levels of 5-8 t/ha/yr. Higher targeted fish production levels of 10-15 t/ha/yr are achieved by resorting to stocking at a density of 15,000-25,000/ha. In carp polyculture, species ratio are maintained for minimizing the inter-specific and intra-specific competition for food available at various trophic levels and zones in a pond. Two or more species occupying different niches could be utilized in a pond for exploiting the food available at various zones. While a combination of six species viz., catla, silver carp, rohu, grass carp, mrigal and common carp has been proved to be the ideal combination for carp culture in India, species combination largely are decided on seed availability and market demand. Of these catla and silver carp are surface feeders, rohu is a column feeder, grass carp is a macro-vegetation feeder, and mrigal and common carp are bottom feeders. A proportion of 30-40% surface feeders (silver carp and catla), 30-35% mid water feeders  (rohu and grass carp) and 30-40% bottom feeders (common carp and mrigal) is commonly adopted depending on the productivity of the pond. PRESENT PRACTICES OF FISH CULTURE IN PONDS  Carp culture The most successful system of pond fish culture is the polyculture of three Indian major carp species - catla, rohu and mrigal along with three Chinese carps viz. silver carp, grass carp and common carp. In India this is commonly known as composite fish culture. The best results in terms of fish production in this system results not only through a judicious combination of species, but also due to appropriate management techniques including pond fertilization, supplementary feeding and health care. On the basis of growth performance of different species, modifications are often made in stocking density, species ratio, fertilization schedule and supplementary feeding programme in different agroclimatic conditions. High rates of fish production to the tune of over 5 500 kg/ha/6 months, 7 200 kg/ha/8 months and over 10 tonnes/ha/yr have been achieved in composite fish culture trials conducted in different agroclimatic conditions of India. The carp culture system as a whole is operated as a three-tier culture system where the practices are adopted for rearing fish during their different stages till they are harvested. Spawn (post larvae) are reared upto fry (2–3 cm) stage in nursery ponds, fry to fingerlings (8–12 cm) in rearing ponds and finally fingerlings to table-size fish in composite fish culture ponds or stocking ponds. Relatively smaller, seasonal ponds are mainly used for rearing spawn to fry stage and harvested after 2–3 weeks. Several crops (3–4) of fry are usually taken during the season. Pond fertilization by cattle manure and feeding with 1:1 mixture of oil cakes and rice bran is the usual practice. Fry raised in nurseries are reared upto fingerlings in slightly bigger ponds (0.05 – 0.1 ha) of seasonal or perennial in nature. Fingerlings are removed after 3 months and stocked in composite fish culture ponds. Integrated carp farming An integrated approach of composite fish culture together with compatible combination(s) with poultry, duckery, pig rearing and cattle raising is now being adopted. Under this system of farming small livestock and farm yard animals, viz. pigs, poultry, ducks, etc., are integrated with composite fish culture by siting animal housing units on the pond embankments in such a way that the animal wastes and washings are diverted into fish ponds for recycling. The fish not only utilize spilled animal feed but also directly feed on fresh animal excreta which is partially digested and is rich in nutrients. Surplus excreta supports the rich growth of planktonic fauna. Fertilizers and supplementary feed are not used, resulting in drastic cost reduction (Sharma et al., 1979; 1979a). Production potential through integrated carp farming is summarised in Table 4. Table 4 Annual production through integrated carp livestock farming Integration Fish production Animal production (live weight) Fish + Pig farming 6 – 7 ton/ha 4 000–5 000 kg pig meat Fish + Duck farming 3 – 4 ton/ha 500 kg duck meat + 17 000–20 000 eggs Fish + Poultry farming 4–5 ton/ha 60 000–70 000 eggs + 1 500– 2 000 kg meat The salient features of the various types of livestock/carp integrated culture systems are described below. Biology, Culture and Production of Indian Major Carps : Introduction. General external features and internal organs of carp. I. Catla catla (Ham.): 1. History. 2. Synonyms, common and vernacular names. 3. Morphology. 4. Colour. 5. Distribution. 6. Age and growth. 7. Length-weight relationship. 8. Food and feeding. 9. Eggs and larval development. 10. Different stages of development. 11. Maximum size of Catla and Harvest. 12. Migration and movement (Spawning/breeding). 13. Seed collection of Catla. 14. Transportation of Fry. 15. Nursery rearing of Spawn. 16. Common diseases of Catla. 17. Control diseases of Catla and their control measures. II. Labeo rohita (Ham.): 1. Taxonomic position. 2. Synonyms, common and vernacular names. 3. Morphology. 4. Colour. 5. Distribution. 6. Occurrence and morphology. 7. Food and feeding habits. 8. Age and growth. 9. Length-weight relationship. 10. Bionomics and life-history. 11. Eggs and larval development. 12. Post-larval stage. 13. Characteristics of advanced Fry and Fingerlings of Rohu. 14. Survival, growth of Spawn, Fry and Fingerlings of Rohu. 15. Fishing season and landing of Rohu. III. Cirrhinus mrigala (Ham.): 1. Synonyms, common and vernacular names. 2. Morphology. 3. Colour. 4. Distribution. 5. Age and growth. 6. Length-weight relationship. 7. Food and feeding. 8. Embryonic and larval development. 9. Growth of Mrigal (C. mrigala). IV. Carp culture: 1. Pre-stocking management of pond or preparation of the pond. 2. Clearance of aquatic weed. 3. Eradication of predator and unwanted trash fish. 4. Fertilization of ponds. 5. Manure. 6. Stocking. 7. Polyculture of Indian major carps and exotic carps. 8. Post-stocking management. 9. Harvest. V. Production of carps through polyculture. Conclusion. References. "Carp culture is an age-old traditional practice in India, which is rich in Carp fauna. The appropriate technology of fish farming evolved through research investigation in Carp culture which has shown a major breakthrough by achieving high yields. Modernization of this technology has uplifted commercial production of carps many folds. The Indian major Carp species Catla (Catla catla), Rohu (Labeo rohita) and Mrigal (Cirrhina mrigala) are considered the best suitable carp species for their cultivable qualities. Thorough knowledge on the biological aspects like food and feeding, growth, maturity, breeding, larval development, etc. are of paramount importance for advanced study of Carps. The above important aspects of Carp biology have been accomplished to a great extent. In polyculture experiments the significant contribution of Indian major Carps in total production when cultured alone or with exotic Carps are well documented. Enormous success in fish production depends mainly on the management practices to be adopted based on sound biological concepts. In this contribution, an attempt has been made to compile the available literatures on biology and culture of Carps with special reference to the modern management practices like pond preparation prior to stocking of Fingerling in optimum density and suitable combination, feeding, harvesting of table sized and replenishing the stock of fingerlings." PEARL A cultured pearl is a pearl created by a pearl farmer under controlled conditions. Pearl Farming Pearl farming is the industry responsible for grafting pearl mollusks and producing cultured pearls. These cultured pearls make up nearly 100% of the pearls sold today. Natural pearls now only account for less than 1/1000th of a percent of the pearls on the market today. What Is Pearl Farming? Cultured pearls are grown on what are known as pearl farms. Several thousand oysters are nucleated and then cared for during the 2-5 years required for a pearl to grow and develop. Like any other form of farming, pearl farming can be as dependent on luck as it is on skill. An entire bed of oysters can be completely devastated by unpredictable and uncontrollable factors, such as water pollution, severe storms, excessive heat or cold, disease and many other natural and man-made phenomena. Although pearl farmers attempt to control as many of these variables as possible, pearl farming can indeed be a risky business Modern Pearl Farming Techniques The first step in the pearl production process is to obtain oysters to be nucleated. In the early days of the cultured pearl industry, oysters were simply collected from the sea. Although some farmers continue using this method today, many use the more modern practice of breeding their own oysters. To do this, the pearl farmer collects oyster sperm and eggs from high-quality oysters already on the farm. The sperm are used to fertilize the eggs, and so create a new generation of oyster larvae. How Oysters Are Raised In Pearl Farming The larvae are allowed to float freely in the water, under controlled conditions, until they are a few weeks old. In the wild, the larvae would then attach themselves to a rock or similar object, so the farmers provide “collectors” for this purpose. Over a period of a few months, the larvae develop into baby oysters. They are generally then moved into a separate "nursery" area of the farm. Here they are tended for around 1-2 years, until they have grown sufficiently large to be nucleated. The Process Of Nucleation In Pearl Farming The process of nucleation is a surgical procedure, whereby a foreign object is implanted into the oyster. This object causes irritation, which the oyster counteracts by secreting nacre to surround the object; this produces the pearl. How Oysters Are Raised In Pearl Farming The larvae are allowed to float freely in the water, under controlled conditions, until they are a few weeks old. In the wild, the larvae would then attach themselves to a rock or similar object, so the farmers provide “collectors” for this purpose. Over a period of a few months, the larvae develop into baby oysters. They are generally then moved into a separate "nursery" area of the farm. Here they are tended for around 1-2 years, until they have grown sufficiently large to be nucleated. Saltwater Nucleation In Pearl Farming Two basic methods of nucleation are used. Saltwater oysters are generally nucleated using a "bead", prepared from mother-of-pearl. First, the bead is surrounded by a small piece of mantle tissue taken from a donor oyster. The bead and tissue are then implanted into the oyster's gonad. The bead serves as a mold, or nucleus, around which the pearl develops. The resulting pearl will contain the bead at its center and will tend to develop in the same general shape as the original bead. The bead can be detected in the final pearl by x-rays. Freshwater Mussel Grafting In Pearl Farming Freshwater mussels are generally grafted using a piece of mantle tissue only, without a bead. This small piece of mantle tissue is placed into an incision in the host mussel's mantle instead of the gonad. Both sides of the valve can accept grafts, and an average freshwater mussel will produce 24 to 32 pearls per culturing cycle. The Pearl Is Now Allowed To Grow After nucleating, the oysters are given a few weeks to recover from the surgery. During this time, some of the oysters may reject and expel the implanted nuclei; others may become sick or even die. Most, however, will fully recover. The oysters are then placed in cages or nets and moved into the oyster bed, where they will be tended as the pearls develop. Depending on the type of oyster, this process can require anywhere from a few additional months to several more years! Finally, The Pearls Are Harvested After the pearls have been allowed to develop fully, they must be harvested. After the pearls are extracted from the oysters, they are washed, dried, and sorted into general categories. Sometimes, the pearls are polished by tumbling in salt and water. The pearls are then sold to jewelers, manufacturers, and pearl dealers. PEARL CULTIVATION The oysters are gathered with the aid of the pearl boat, which serves as the divers' platform and transports several thousand live oysters in its holding tanks. There are two long booms (about 10 metres long) that extend out from the side of the boat, each holding towropes. With the aid of the booms, as many as six divers can operate simultaneously on the bottom of the ocean floor at depths of seven to 20 metres and cover an area 20 metres across as the boat drifts along with the tide. On board the pearl boat, the oysters are counted, cleaned and weighed, then placed in a window-sized metal frame between layers of nylon netting. The panels hold between six to nine shells. The oysters are then transported in a saltwater tank to a holding area, where the frames are attached to the sea bottom in order to recover from the stress of their capture. The Seeding of the Oyster In a few months the panels are lifted back onto the boat where the oysters are opened and seeded by a technician. The technicians - predominantly Japanese - have honed the implantation process to a delicate art form. The process involves inserting into the oyster a nucleus and a tiny piece of mantle cut from a nearby oyster; the nucleus is made with shell taken from a North American mussel and the mantle is the part of the fleshy oyster lip that secretes the nacre. It has been found that the shell of the North American mussel is the best material for the pearl nuclei because it is least likely to be rejected by the oyster. However, due to the great demand within the industry for them, the mussel shells are very expensive. Once the seeding process is completed, the oysters are quickly returned to the holding area in their panels for further convalescence. Several months later the shells are transported, sometimes up to 2,000 nautical miles away, to remote farming bases. ThePearlFarm The pearl farms are best located in sheltered areas with active tides. The north coast of Western Australia has proved to be an ideal location: there is scarcely any water pollution, few people, and extremely good tides as high as 10 metres. The big tides feed the oyster a rich mixture of organic food.These locations are also chosen for their geographical protection from cyclones which is a climate hazard of the north west.Once here, the oyster shells are suspended from culture systems; the panels holding the shells are hung on long lines, like underwater clotheslines, supported by buoys. They are tended daily by farm workers who carry out the intensive husbandry required for the next 20 to 24 months. The oysters are cleaned to keep them free of marine growth and, occasionally, even hauled up for x-ray to assess their progress. ThePearlHarvest The pearls are harvested during the months of June and September. Once the pearls have been taken out of the oysters, they are initially sorted, usually by shape and size. The oysters are seeded anew and the cycle begins again. A healthy oyster can be reseeded as many as four times with a new nucleus. As the oyster grows, it can accommodate progressively bigger pearl nuclei. Therefore, the biggest pearls are most likely to come from the oldest oysters. Unproductive oysters are still valuable: the nacre-covered inside is marketed as mother-of-pearl and its dried meat sold overseas in such places as Hong Kong and Shanghai, where it is considered a delicacy. The cultivation process for freshwater pearls is very similar with the following exceptions: Freshwater pearls are cultivated in mussels. Freshwater pearls are farmed in lakes and rivers, predominantly in Japan and China. During the implantation process, only mantle tissue is inserted into the mussel. In contrast to saltwater oysters, these mussels can produce 10 or more pearls at once by inserting the required number of mantle tissues. Freshwater mussels do not need to be cleaned at all once they are returned to the pearl farms. The harvesting period is shorter. Freshwater mussels are not reseeded as many times as saltwater oysters. Development of a pearl A pearl is formed when the mantle tissue is injured by a parasite, an attack of a fish or another event that damages the external fragile rim of the shell of a molluc shell bivalve or gastropod. In response, the mantle tissue of the mollusk secretes nacre into the pearl sac, a cyst that forms during the healing process. Chemically speaking, this is calcium carbonate and a fibrous protein called conchiolin. As the nacre builds up in layers of minute aragonite tablets, it fills the growing pearl sac and eventually forms a pearl. It is a myth that a grain of sand can cause a pearl to form, as nacre will not adhere to inorganic substances. Natural pearls are those pearls that are formed in nature, more or less by chance. Cultured pearls, by contrast, are those in which humans take a helping hand. By actually inserting a tissue graft of a donor oyster, a pearl sac forms, and its inner side precipitates calcium carbonate in the form of nacre.  The pearl industry Modern-day cultured pearls are primarily the result of discoveries made in the late 19th and early 20th centuries by the Japanese researchers Mise and Nishikawa. Although some cultures had long been able to artificially stimulate mollusks into producing a type of pearl, the pearls produced in this way were only blister and mabe, rather than actual round pearls. What Mise and Nishikawa discovered was a specific technique for inducing the creation of a round pearl within the gonad of an oyster. This technique was patented by Kokichi Mikimoto shortly thereafter, and the first harvest of rounds was produced in 1916. This discovery revolutionized the pearl industry, because it allowed pearl farmers to reliably cultivate large numbers of high-quality pearls. In contrast to natural pearls—which have widely varying shapes, sizes, and qualities, and which are difficult to find—cultured pearls could be "designed" from the start to be round and primarily flawless. The oysters could be monitored for up to two years until each pearl was fully formed, thus better ensuring their health and survival. And the pearls could be produced by the tens of thousands, thereby bringing their cost down to a point where pearls became accessible to large numbers of people around the world. In short, the development of cultured pearls took much of the chance, risk, and guesswork out of the pearl industry, allowing it to become stable and predictable, and fostering its rapid growth over the past 100 years. Led by pearl pioneer John Latendresse, the United States began culturing freshwater pearls in the mid 1960's. Today more than 99% of all pearls sold worldwide are cultured pearls.Cultured pearls can often be distinguished from natural pearls through the use of x-rays, which reveals the inner nucleus of the pearl. Freshwater pearls are pearls which grow in non-saline environment in freshwater mussels. Where Do Freshwater Pearls Come From? Although the traditional source of pearls has been saltwater mollusks, freshwater mussels, which live in ponds, lakes and rivers, can also produce pearls. China has harvested freshwater pearls in the form of mabe since the 13th century, and has now become the world's undisputed leader in freshwater pearl production. The first record mentioning pearls in China was from 2206 BC. The United States was also a major source of natural freshwater pearls, from the discovery of the New World, through the 19th century, until over-harvesting and increasing pollution significantly reduced the number of available pearl-forming mussels in the US. The Appeal of Freshwater Pearls Generally speaking, freshwater pearls are not as round as saltwater pearls, and they do not have the same sharp luster and shine as akoya pearls. However, they appear in a wide variety of shapes and natural colors, and they tend to be less expensive than saltwater pearls, making them very popular with younger people and designers. Also, because freshwater pearls are solid nacre, they are also quite durable, resisting chipping, wear, and degeneration. China Leads The World In Freshwater Pearl Production With a total production of 1,500 tons in 2006, China holds a monopoly over the pearl industry today. Although the birth of the Chinese freshwater pearl industry is traced back to the area around Shanghai, freshwater pearls are now produced in all the surrounding provinces including: Zhejiang, Anhui, Jiangsu, Hubei, Hunan, and Jianxi. Local pearl trade is conducted mainly in the cities of Zhuji (Shanxiahu), Suzhou, Wuxi, Wenling, and Weitang. The largest marketplace for these freshwater pearls is the world's pearl trading hub, Hong Kong. What Makes Freshwater Pearls Different? Freshwater pearls differ from other cultured pearls, in that the great majority of them are not bead-nucleated. Freshwater mollusks are nucleated by creating a small incision in the fleshy mantle tissue of a 6 to 12 month old mussel, then inserting a 3mm square piece of mantle tissue from a donor mussel. Upon insertion, the donor, (graft) tissue is twisted slightly, rounding out the edges. What happens after this point is really just speculation. Some believe that this tissue acts as a catalyst in producing a pearl sac thus making the 'nucleation' actual 'activation'. Others believe the tissue molds with the host to create a pearl sac, while still others maintain the tissue is the actual nucleus. Although it is said that a freshwater mollusk can withstand up to 25 insertions per valve, it is common industry practice to perform only 12-16 insertions in either valve, for a total production of 24-32 pearls. The mollusks are then returned to their freshwater environment where they are tended for 2-6 years. The resulting pearls are of solid nacre, but without a bead nucleus to guide the growth process the pearls are rarely perfectly round. What Makes Today’s Freshwater Pearls So Much Better? The major increase in quality can be attributed to several factors. The primary jump in quality was accomplished when the industry shifted from the Cockscomb pearl mussel, (Cristaria plicata) to the Triangle shell, (Hyriopsis cumingii) in the middle 1990's. The Cockscomb was responsible for the low-quality rice-crispy pearls of the 1970's and 1980's. Another shift in quality can be attributed to the lower number of grafts inserted into either valve. This number has dropped by an average of 5 per side in the last decade. The turn of the century brought another wave of quality and exotic pearl colors in the form of mussel hybridization. Japans Freshwater Pearl Industry, a Rough History The Japanese have a distinguished history of culturing freshwater pearls as well. Lake Biwa was once world renowned for producing high-quality freshwater pearls produced by the Hyriopsis schlegelii, (Biwa pearly mussel) mussel. However, in the mid 1970's pearl farming all but came to a halt due to pollution in this lake that was once synonymous with freshwater pearls. The Japanese tried once again to farm freshwater pearls in Lake Kasumigaura in the last decade, utilizing a bead-nucleated hybrid mussel (Hyriopsis Schlegelii/Hyriopsis cumingii). The resulting pearls have been quite large and unique. The Kasumiga pearl industry had a very short life span, however, with production ceasing in 2006. The industry is once again a pollution fatality of Japanese industry. The remaining Kasumiga pearls are exclusively sold by the Belpearl pearl company. Saltwater Pearls A saltwater pearl is a pearl produced by a saltwater mollusk in a saline environment. Traditional Saltwater Pearls Traditionally, most pearls were gathered from saltwater-dwelling mollusks in the Persian Gulf, the Red Sea and the coastal waters of India and Japan. These saltwater pearls were referred to as marine pearls. Natural saltwater pearls are still found, but the yield is too small to account for any significant market share. AustralianPearls The Australian South Sea Pearl is unquestionably the rarest and finest cultured pearl in the world. No other pearl can equal its natural beauty and size. These high grade Australian Pearls are of such quality they do not require bleaching, tinting, dying or skinning. Their beauty will never fade because they are pure and untreated, ensuring a treasure that can be passed down from generation to generation. Australian pearls range in size from 8mm up to 18mm, and come in many varied shapes and colours. The highly prized 'round' and 'drop' pearls are only two of the many natural shapes available. Baroque, circled, button and keshi pearls may be unique shapes, but all possess a beauty and style of their own. Like their 'round' and 'drop' counterparts, these pearls are naturally coloured silver, white, pink, golden or blue. Australian Pearls are highly prized and generally the most expensive. South Sea Pearls There are two basic groups of South Sea cultured pearls: white and black. Pearls from the white group are primarily cultured in the northern waters of Australia, the Philippines and Indonesia. Their rarity and exceptional sizes, from 8 to 20mm, make them highly prized. Their colours range from white and silvery blue to pale gold - the golden or light-yellowish varieties abound in Philippine and Indonesian waters while white or silvery hues occur mainly in Australian waters. Pearls from the black group, among which is the legendary black pearl of the South Pacific, are most frequently found over a wide area stretching from the Cook Islands, eastward through Tahiti to the Tuamotu Archipelago and the Gambier Islands in French Polynesia. Tahitian Pearls   The cultured pearl of Tahiti is synonymous with magic and perfection. Most come from the atolls and lagoons of the South Pacific. They tend more toward drop shapes than round and vary in size from 7 to 15mm. They can be black, silver, dark or light grey. The rarest colour is "peacock green" - the greenish black colour of a peacock feather. Akoya Pearls Considered the classic amongst cultured pearls, Akoya Pearls are primarily round or oval in shape and measure 2 to 10mm. They are cultured in southwestern Japan and China. Their colours range from pinkish white to creamy shades and silvery blue. Keshi Pearls  Possessing a whimsical charm entirely different to the perfectly round, large pearls, seedless keshi pearls arise spontaneously in the culture of Akoya, and South Sea pearls. These small freeform pearls make fascinating necklaces in colours ranging from silvery white to silvery grey. Mabé Pearls Mabé Pearls are attractive half pearls with beautiful, rainbow-coloured iridescence. The pearl was named after the mabé pearl oyster which is found mainly in the tropical seas of Southeast Asia and in the Japanese islands around Okinawa. Since the beginning of the century, many attempts had been made to cultivate round pearls from the mabé oyster but all had failed. However, in the 1950s hemispherical pearls (or 'half pearls' as they are more commonly known) were successfully cultivated. Today, most of these cultured half pearls do not come from the mabé oyster, but rather from the South Sea's silver-lipped oyster. Mabé pearls are also available in oval, cushion, drop and heart shapes. Chinese Freshwater Pearls Chinese Freshwater Pearls are grown in an amazing variety of delicate shapes ranging from round and oval to button, drop and baroque. Their colours vary from pure white to orange and rosy violet. Kasumiga Pearls The Kasumiga is a new type of pearl that comes from a lake northeast of Tokyo. The mussels are a crossbreed between Japanese and Chinese freshwater mussels, and are implanted with round or flat seeds. Kasumiga Pearls glow in rosy hues of light to dark pink. Valuing pearls The most important factors taken into consideration when valuing cultured pearls are lustre, colour, shape, surface and size. Lustre The most important indication of a pearl's quality is lustre. The lustre of a pearl refers to the glowing appearance of its surface, and is judged by it brilliance and ability to reflect light. A pearl with a high lustre will be very shiny and show reflections like a mirror while a pearl with poor lustre will appear very milky or chalky. Lustre is determined by the quality of a pearl's nacre-its transparency, smoothness and overall thickness. Factors affecting the quality of the nacre include the cultivation place, the health of the mother oyster, the length of time spent in the oyster, pollution and the type of oyster used. Only strong layers of nacre can produce deep lustre.It is better not to compromise on lustre as this feature cannot be hidden or enhanced by its jewellery mount. Colour Pearls present a whole palette of colours to choose from. Light coloured pearls are produced in shades of white, pink, silver, gold and blue, while dark coloured pearls range from peacock green and aubergine purple to all the shades of grey. Above all, a pearl's colour is a question of personal taste. Although some shades are especially rare or popular and therefore highly valued, such as rosy white, silvery white and pale gold, the colour of a pearl is certainly not an indication of its quality. Shape The shape of a pearl plays a major role in determining its value. Pearls can be divided into four basic groups of shape. These are in order of value: Round Off-round Slightly round or ovalish Semi-baroque Not round. Some examples are pear, drop, egg and button shapes. Baroque Very irregular in shape with a surface that is often very uneven, occasionally resembling teeth, cacti, tadpoles and mushrooms Throughout history, the round pearl has been considered the most valuable and popular shape. However, most of the world's most famous and valuable pearls are often not symmetrical in shape, and that is because the other grading factors are also important. Shape is a good category to compromise on if you need to cut down on price. Actually, baroque and circled pearls can make for very interesting jewellery pieces. Surface The fewer the spots or blemishes a pearl has, the higher its value. But again flaws can also be positive features. They may serve as identifying marks that a pearl is yours and not somebody else's, and help prove that it is real and not imitation.Flaws can also lower the price of a pearl without necessarily affecting its overall beauty. Size The size of a pearl is expressed in terms of its diameter, which is measured in millimetres. Size has a significant impact on price. One millimetre's difference has been known to raise a price by between 100 and 200 per cent.