We cloned and characterized the full-length fibroin gene of Antheraea yamamai (Lepidoptera, Saturniidae) from Japan and compared the sequence with that of A. yamamai from Korea. While the sequence of 5’-flanking region was highly conserved, the repetitive sequence units were quite different in number and arrangement; therefore, the gene length differed between them. Furthermore, we conducted genomic Southern blotting to assess the length polymorphism of fibroin genes using 11 samples of A. yamamai from 9 locations in Japan. We also amplified a DNA fragment covering a nonrepetitive region of the fibroin gene corresponding to the 5’-flanking, first exonic, intronic, and partial second exonic sequences from each sample and then sequenced. As a result, we detected extensive gene-length polymorphism in A. yamamai, which is likely associated with expansion of repetitive sequences by unequal recombination events, although the sequences in non-repetitive regions were highly conserved.

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　　Silk gland fibroinase is cathepsin L-like cysteine proteinase obtainable from insect silk gland. At each larval molt period, it is secreted into the lumen of silk gland and digests both fibroin and sericin. It thus ensures silk gland cells in the next larval instar to synthesize and secrete fibroin and sericin into the lumen of silk gland. In early pupal stage, fibroinase secreted into the lumen of remaining silk gland digests remaining fibroin and sericin to help apoptosis of silk gland. In the feeding larvae, fibroinase is localized in lysosomes in silk gland cells to digest proteins and organelles there.

　　Fibroinase was purified first from the domesticated silkworm, Bombyx mori and then from wild silkmoth, Samia cynthia ricini. These fibroinases were different in some properties. N-terminal amino acid sequence was slightly different. It may be related to molecular structure of its substrate, fibroin. S. cynthia ricini fibroin is consisted of alternate sequences of poly-Ala and repeated Gly-Ala motif. B. mori fibroin is consisted of repeated Gly-Ala motif only. In the fifth instar larval period, S. cynthia ricini fibroinase increases its activity one day after onset of spinning and reaches maximum at end of spinning. B. mori fibroinase increases its activity before onset of spinning and reaches maximum at larval-pupal ecdysis. Maximum absolute activity of S. cynthia ricini fibroinase is 38 times higher than that of B. mori fibroinase. Silk gland of S. cynthia ricini degenerates to disappear after one day of end of spinning. B. mori silk gland remains after two days of larvalpupal ecdysis. Thus silk gland fibroinase can be a molecular tool to study species specificity of silk spinning insects.

　　Fibroinase can beautifully digest sericin in addition to fibroin as seen in the lumen of silk gland at each larval molt period. Fibroinase can be utilized as a new agent for enzymatic degumming of silk. Silkworms instructed this wisdom through fibroinase study of more than 20 years.

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Back cross with Daba TV (DTV) (donor and non-recurrent female parent) and Andhra local (recipient and recurrent male parent) ecoraces of Antheraea mylitta Drury revealed significant improvement in productivity indices of Andhra local (AL) having high commercial characters and low survival rate. Mating incompatibility of Andhra local with other eco races under captive conditions was minimized to 15.33% by achieving 84.67% of natural pairing under insitu grainage model. Significant positive heterosis (MPV) and heterobeltiosis (BPV) were expressed by Back cross – IV (BC-III×AL) hybrid for fecundity (13.00% and 4.65%), survivability (101.21% and 22.00%), silk ratio (7.40% and 3.11%) and reelability (1.58% and 7.25%) characters when compared to F1 (DTV×AL), Back cross – I (F1×AL), Back cross – II (BC-I×AL) and Back cross – III (BC-II×AL) hybrids. The high degree of variability in parental eco races and expression of heterobeltiosis in resultant hybrids can be exploited commercially.

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　　The lustrous golden yellow silk produced by muga silkworm Antheraea assamensis (Helfer) is pride of India and endemic to North Eastern region in general and Brahmaputra valley in particular. The annual muga silk production in the country is 119 MT and major share comes from Assam state alone (99.0%). Though there is a great scope for improvement in terms of raw silk production and productivity, the industry is suffering from inherent problems i.e., such as poor performance of pre seed and seed crops in traditional states due to hostile climatic conditions that effects the timely supply of quality dfls in required quantities.

　　The attempts made by scientists of RTRS, Warangal in Chintapalli, Visakhapatnam district of Andhra Pradesh, a non traditional state reveals that the productivity in pre seed and seed crops is ranged between 50-68 cocoons/dfl against 12 to 25 cocoons of traditional state. The dfl multiplication ratio is in the range of 1:12 to 1:16 against 1:5 and 1:15. The rearing and grainage performance reveals that there is a great scope to develop Chintapalli in Visakhapatnam district of Andhra Pradesh as seed zone. Similarly Doon valley, Haldwani and Bhageshwar in Uttarakhand may also supplement the seed requirement of Assam during unfavorable season.

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DNA analysis of different nature grown ecoraces of Antheraea mylitta Drury at Centre for DNA finger printing and Diagnostics (CDFD), Hyderabad, India had suggested seven potential hybrids for evaluation at different tasar zones in India. In the present studies, three hybrids and reciprocals viz. Andhra local (AL)×Bhandara local (BL), Bhandara Local (BL)×Andhra Local (AL), Andhra local (AL)×Daba TV (DTV), Daba TV (DTV)×Andhra local (AL), Bhandara local (BL)×Daba TV (DTV) and Daba TV (DTV)×Bhandara local (BL) were evolved by using three parents. Andhra local, Bhandara Local and Daba TV. Out of six combinations tested for eight yield components, Andhra local×Bhandara local (AL×BL) which was also recommended by CDFD, Hyderabad expressed positive heterosis and heterobeltiosis significantly for natural pairing (30.48% and 22.35%), fecundity (37.50% and 11.24%), survivability (205.00% and 188.36%), shell weight (23.08% and 13.27%) and silk ratio (12.74% and 10.46%). The ecoraces Andhra local and Bhandara local should be conserved in their respective natural habitat to exploit hybrid vigor for commercialization.

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Tasar silkworm is an economically important species. Because it is a wild species, egg production depends on mate finding and oviposition by females. Light and scanning electron microscopic study reveals presence of large number of hair sensilla on the ovipositor of Antheraea mylitta, which influences oviposition behavior. Three types of sensilla, hair sensilla, papillae and microtrichia are prominently observed on the ovipositor, which play their role in oviposition as mechanoreceptors and chemoreceptors.

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India has unique distinction of producing all varieties of silks namely, mulberry, eri, tasar and muga. India is the only country where tropical tasar silk is produced. The beautiful wild silks (Vanya silks) with special reference to tasar, due to immense diversity in climatic conditions coupled with wide- ranging ecological habitats. The country stands second largest tasar silk producer in the world after China. The preservation of the biodiversity is the most important global challenge of the present day. The combined efforts of the forest, tribal welfare and the department of Sericulture along with the local tribal rearers should be made for the protection and the conservation of wild silk moths.

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Eri silkworm, Samia ricini (Donovan) is a domesticated multivoltine nonmulberry silkworm and one of the major component of wild (Vanya) silk of India. This insect has been exploited commercially for its silk since time immemorial. Brahmaputra river valley of Assam is considered as original home of cultivated eri silkmoth. There are two species of eri silkworms available in North - East India, viz., the domesticated Samia ricini and its wild progenitor Samia canningi (Hutton). The silk produced by eri silkworm is considered economically the third most important silk in the world after mulberry silk and Chinese Tasar. Northeastern region of India is rich in genetic resources of eri silkworm and numbers of eco-races are existing in nature. Out of 19 species of eri silkworm under genus Samia all over the world, S. ricini (cultivated), S. canningi (wild) and S. fulva (Jordan) are reported to be found exclusively in India. The present paper deals with maintenance of germplasm bank of 26 cultivated eri silkworm eco-races with one wild race of eri silkworm collected from different parts of N.E. India, listing of passport data, morphological characterization, evaluation and development of hybrid with better potentiality. Hybrid worms of wild eri ♀ (S. canningi)× cultivated eri ♂ (S. ricini) reared successfully four consecutive generations. The maximum fecundity (364.6±5.03) and hatching percentage (83 ±2.55) was recorded in F3 generation on Heteropanax fragrans and highest cocoon weight (3.40±0.11), pupal weight (2.98±0.12) and shell weight (0.41±0.02) were recorded in F2 generation on Heteropanax fragrans.

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A phagostimulant formulation H1 was fortified with different combinations of ascorbic acid, proline and Na cyclamate to study their effect on growth and development of Muga silkworm under indoor rearing. All the chemicals fortified with formulation H1 had positive effect on body tissue growth of Muga silkworm, the best fortified combination being ascorbic acid–proline that gave highest average tissue growth of 2.8861 g against the average tissue growth of 2.55934 g in control. In larval survivability, the fortified nutrient combination ascorbic acid–proline and ascorbic acid–Na cyclamate had profound effect in all the instars. In respect of cocoon qualities, measured as cocoon weight, shell weight and silk ratio, all the nutrient combinations with phagostimulant formulation H1 were high in contrast to control. Leaf extract of Som (Persea bombycina Kost) plant has positive effect if used in the spray solution as substitute of blank water.

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In the present study a technique for the isolation of embryo for the muga silkworm has been developed. Muga silkworm eggs are first fixed in hot water at 90℃ for 10 minutes. The fixed embryo inside the egg is isolated with the help of a surgical blade (No.12) fitted with handle, a fine needle and a forceps under dissecting binocular microscope. The isolation of embryo is carried out under water in a petridish. The fixed eggs are preserved at 4% acetic acid and isolated for embryonic studies. With this technique the fixed eggs can be preserved for 2 years and the embryo remains intact inside the preserved eggs and can be isolated at later date as required. With the present technique the earliest morphologically identifiable stage i.e. stage 4 can be isolated. The other technique using carnoy, formaldehyde and KOH do not yield satisfactory results.

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The study shows that if the non mulberry yarn treated with low pressure air plasma treatment, the properties like dye uptake, wicking were improved significantly. There will not be any effect of plasma treatment on tenacity and elongation on non mulberry silk fibre. Surface morphology can be improved by removing the rough surfaces.

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Eri silkworm Samia ricini (Donovan) is a polyphagous insect and the farmers of North East India rear the silkworm mainly on two primary host plants viz., Castor Ricinus communis L., and Kesseru Heteropanax fragrans Seem., for production of cocoons and pupae. The micro-climate around Kesseru leaves, topography of the leaf surface and the typical leaf exudates influence the growth and development of varieties of leaf surface microorganisms. The phylloplane mycoflora play important role in supplying different types of nutrients to the plants as well as to the silkworm. During the study on the phylloplane mycoflora of Kesseru on three different types of leaves viz., tender, semi mature and mature, nine fungi were recorded, isolated and identified during autumn while seven fungi were isolated and identified during winter season. Aspergillus fumigatus was the dominant and Alternaria alternata was the co-dominant species found in both the seasons while Mucor sp., Curularia sp., Fusarium sp., Helminthosporium sp., Candidus sp., Penicillium sp. and Cercosporella sp., showed less percentage of occurrence. Evaluation on the rearing performance of Eri silkworm during the corresponding seasons revealed 84.50% hatching, 74.87% ERR and 14.56% SR in autumn as compared to 82.50%, 76.82% and 13.99% respectively in winter season. Assessment on cocoon and yarn quality revealed higher shell weight (0.38 gm), lesser degumming loss (8.00%), higher yarn count (8.25 nm) with higher yarn recovery (80.00%) during autumn, while during winter shell weight, degumming loss, yarn count and yarn recovery were recorded as 0.36 gm., 8.00%, 20 nm and 78.00% respectively. The occurrence of fungal species was more dominate in the autumn season with comparatively better rearing performance and economic traits during the period as compared to winter season.

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Borduar ecorace of eri silkworm was reared on Castor, Ricinus communis Linn, Kesseru, Heteropanax fragrans Seem, Tapioca, Manihot utilissima and Barpat, Ailanthus grandis in two favourable seasons, Autumn (Sept.-Nov.) and Spring (Feb.-April) to study the reproductive as well as ovipositional behaviour of eri silkmoth with respect to different food plants. Moth emergence pattern, single moth weight, wing span of a single moth were studied after feeding with foliage of four different host plants and Castor, Ricinus communis was found to be most suited host plant for eri silkworm in all aspects. The percentage of unemerged cocoon was comparatively less in case of Castor than that in other food plants. Both potential and effective fecundity in terms of eggs, egg size, fertilization of eggs and hatching were found higher in case of Castor. In all aspects, Tapioca and Barpat were found less suitable than Castor and Kesseru. Further, Tapioca was found least suitable among all the four food plants studied in all other aspects except egg size which is bigger in Tapioca than Barpat.

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Mated female eri silkmoths, Samia ricini Donovan were tied on numberd Kharika and kept in four environments viz. I (continuous 24 h dark), II (continuous 24 h light), III (alternate scoto, 12 h- photo, 12 h period) and IV (control) at 27.5ºC-28.5ºC temperature and 60-70% R.H. It was observed that females laid maximum eggs in environmental condition I. In condition II, eggs were laid minimum and in irregular fashion, than conditions I, III and control.

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Cricula trifenestrata Helfer is a wild golden silk producing moth and grows in natural conditions in the eastern and north-eastern parts of India. It is also reported as a pest of different host plants in other parts of the country. The present report highlights the life cycle in new food plants i.e. Indian olive, som, soalu, black berry, mango, cashew and dighloti. The behavior of egg, newly hatched worm, different instars, cocoon formation, post cocoon parameters and other related attributes were recorded on different host plants. The mean performance of rearing, four crops in a year indicates that single cocoon weight varied from 1.28–2.37 g, single shell weight, 0.103–0.127 g and silk ratio, 5.370–8.196%, respectively. The post cocoon parameters indicate that the cocoon is not reelable but spinning is possible like other cultivated silkworms. Even ghicha thread can be prepared for rough dress materials. The insect is hardy in nature and can survive in adverse climatic conditions superseding the cultivated silkworms. This insect is polyphagous and some new food plants have been reported for the first time from this part of the country. The conservation and utilization of Cricula have been highlighted in this paper.

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