LECTURE 11: MORPHOLOGY AND BIOLOGY OF LAC INSECT AND DIFFERENT STRAIN. 1. Degree Programme: B. Sc (Ag) 2. Year: 3rd 3. Semester: VI 4. Course Name: Management of Beneficial Insects 5. Course Code: AEZ-302 6. Topic Name: Morphology and biology of lac insect and different strain. 7. Date: 27.03.2020 8. Course Instructor: Mr. G. S. Giri, Dr. Neeraj Kumar, Dr. R. Prasad INTRODUCTION The word lac is derived from the sanskrit word laksha, which represents the number 100,000. Lac is the harden secretion or outer protective covering of lac insect. The insect produce three products namely resin, dye and wax of great commercial importance. The resin commonly called lac and is the only product of animal origin. It is commercially available in the market as shellac or seedlac or button lac. TAXONOMY Lac insect : Laccifera lacca Order : Hemiptera Sub order : Homoptera Super family : Coccoidae Family : Kerridae Genus : Laccifera Species : lacca DISTRIBUTION India, Pakisthan, Sri Lanka, Myamar, Malaysia, China, Thialand MORPHOLOGY Lac insect is a hemimetabolous i.e. it undergoes gradual metamorphosis. It has three life stage namely egg, young one and adult. The young ones are called as nymph. The nymphs are similar to adult in all aspects except their size and reproductive organs. The adult male and female are different from each other. Female is about three time larger than the male. Male: These are pinkish red in colour and may be winged or wing less. Winged male possesses only one pair of translucent membranous forewing. They are mostly found during dry season (Baisakhi and Jethwai). They survive for 3 to 4 days only and die after coupulation. Some of the important characteristics are i. Head is large, prominent mouthparts but vestigial ii. Ocelli are two pairs with seven segmented antennae which have hair on them. iii. Tarsi 3 segmented. iv. The abdomen is 8 segmented, broader anteriorly and narrower posteriorly. v. The last abdominal segment bear pointed penis. Female: The female is pinkish in colour. The ventral surface of body is flat while dorsal surface is convex. Some of the important characteristics are i. The female have degenerated eye, legs and wings. ii. Antennae are vestigial, small and 3 to 4 segmented. iii. Mouthparts are piercing and sucking type, rostrum is two segmented. iv. Mesothorax is provided with an appendage on which spiracles open. v. The abdomen is round and on the dorsal surface, a spine is provided. BIOLOGY Lac insect lives in cavities or cells made in the resin or lac secreted by them on their host plant. On an average, a female lays 200 - 500 ready to hatch eggs i.e. the embryos are fully developed inside the eggs when they are laid. In other words we can say that lac inset have ovoviviparous mode of reproduction. La insects laid three types of eggs, i) from which male are emerge in large number as compared to female, ii) from which female are emerge in large number as compared to male iii) from which both male and female are emerge in same number. The eggs hatches with in few hours of laying and the tiny crimson-red first instar nymphs come out of the lac encrustation. The nymphs possess a pair of antennae, three pairs of legs, two compound eyes and six anal setae. The first instar nymphs are called as crawler. The emergence of nymph is called as swarming which may be continuing for five or more weeks. The nymphs crawl about on the branches for some time and on reaching soft, succulent twigs, settle down, thrust their needle like proboscis into the bark and start sucking the sap. Usually the nymphs choose twigs that are neither too tender nor too hard and settle close together at the rate of some 200-300 insects per inch depending upon the number of broods. After a days or so on settling, the nymph starts secreting resin from the gland distributed under the cuticle all over the body except near the mouthparts, the two breathing pores and the anus. The resin when secreted is in a semi solid condition, it hardens on exposure to air into a protective covering which we called the lac. The nymphs moult thrice inside the cells before reaching maturity, the duration of each instar being dependent on several factors such as temperature, humidity and host plant. After the first moult, both male and female nymphs lose their legs, antennae and eyes become degenerate but anal setae becomes 10 instead of 6. The male and female cell become distinguishable at this stage itself, the male being slipper like with an operculum at the rear end and the female become nearly globular. While still inside their cells, the nymphs cast off their second moult, pass through a kind of prepupal and pupal stage during which the male regenerate their appendages, whereas female stay as degenerate forms, but feed, grow in size and secret resin. After third and final moult, the male emerged as winged and wingless adults. The male takes half of the time of the female to mature and their dimorphism ends in the second generation when only wingless forms are born. They are unable to feed due to atrophy of their mouth parts and soon after their emergence, they start mating with as many females as possible and die after that. The female remain inside their lac cells and start growing at a faster rate. Their cells increase in size so that bulk of the lac is contributed by the females. As they grow, they become globular filling the entire space of the lac cell. When they are about to lay eggs, they shrink in size providing space for the eggs. At this time, two yellow spots appear at the rear end of the cell. The spot enlarged, become orange coloured. When this happens, the female have oviposited a large number of eggs in the space called ovisac under the tail ends. The ovisac full of eggs appears orange which indicates that the egg will hatches within a week of time. At this stage, the twigs (brood lac) are cut from the tree for the purpose of inoculation to new trees. HOST TREE AND STRAIN Host of major importance 1. Palas – Butea monosperma 2. Ber – Zizyphus mauritiana 3. Kusum – Shorea oleosa 4. Kher - Acacia catechu Other host tree includes Cajanus cajan (Arhar), Acacia auriculiformis (Akashmani), Zizyphus xylopyra (Ghont), Ficus sp., Grewea sp., Acacia Arabica (Babul). STRAIN OF LAC INSECT Lac insect Rangeeni Kusumi Aghani(6 month) Jethwi(6 month) Katki(4 month) Baisakhi(6 month) Inoculation Inoculation Inoculation Inoculation June-July Jan-Feb June-July Oct-Nov Harvesting Harvesting Harvesting Harvesting Jan-Feb June-July Oct-Nov June-July The host tree can be divided into three categories based on the type of strain Tree on which only kusumi strains can be developed : Shorea oleosa (kusum) Tree on which only rangeeni strains can be developed : Butea monosperma (palas) Tree on which both kusmi and rangeeni strain can be developed : Zizyphus mauritiana (ber), Acacia auriculiformis (akashmani), Acacia catechu (khair), Ficus sp. Albizia lucida (Galwang) and Flemingia semialata are introduced species of plant on which lac cultivation can be taken up on plantation basis. .