Antheraea mylitta Drury is a polyphagous, semi domesticated tropical tasar silk insect which feeds on a number of food plants available in the forest. The fifth instar larva is the most crucial stage for growth and post larval life. So, the growth parameters like length, breadth and weight of fifth instar larva was evaluated in different seasons at different altitudes. Significantly the highest values of growth parameters were recorded in the larvae raised on Asan (Terminalia alata W. & A.) food plant at both the lower and medium altitudes during autumn season as well as at lower altitude during winter season. Basing on growth performance of the fifth instar larvae of A. mylitta, the eight food plants considered for study during autumn season at both the lower and medium altitudes were graded in the order Asan > Sal > Arjun > Ber > Sidha > Dha > Bahada > Jamun. However, the eight food plants chosen for study during winter season at lower altitude were graded in the order Asan > Arjun > Sal > Ber > Sidha > Dha > Bahada > Jamun on the basis of larval growth performance.

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UV absorption activity of sericin extracted from cocoons of wild silkmoth, Fagara (Attacus atlas Linn.) and Eri silkworm (Philosamia ricini) together with sericin extracted from cocoons of domesticated silkworm, Bombyx mori, bivoltine strain (W7) and polyvoltine strain (Nang noi) were investigated. Sericin extracts were prepared by immersing cocoons in a boiling distilled water bath. Crude sericin extracts were salting out with 50 % (NH₄)₂SO₄ and centrifuged. The resultant supernatants and precipitated fractions were analyzed for protein concentration by Bradford assay, molecular mass estimation by SDS-PAGE and UV absorption by ultraviolet-visible spectrophotometry. The sericin extracted from wild silkmoths, Fagara and Eri silkworm, showed higher UV absorption activity (λ_max 200 nm) than the domesticated silkworms, both bivoltine and polyvoltine strains. The precipitated protein fractions of all cocoon types showed higher UV absorption activity (λ_max 200 nm) than proteins remaining in the supernatants. This study disclosed that Fagara silk sericin has the potential in UV absorption particularly at UVC wavelength (200 nm).

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Cordyceps is fungus that contains cordycepin, which can be used for medicine or supplementary. Under normal conditions, they infect and grow on insects, especially from the order Lepidoptera, but for commercial purposes, development of Cordyceps media based on locally abundant plant substrates is warranted. Here we investigated various fungal media based on different plant substrates supplemented with pupal powder obtained from Thai silkworm, Bombyx mori. Four strains of Cordyceps militaris (17944, 17991, 18247, 27815) and Paecilomyces tenuipes were grown on sticky rice, black rice, brown rice, rice, rice bran, corn, taro, soybean, and peanut, each mixed with 5 g of pupal powder at 24-25 ℃, 80-90 % relative humidity. Beauveria bassiana was used as positive control. Effective recipes for mycelial growth all types of rice with pupal powder, but not in any of other plant substrates with pupal powder. The largest growth of mycelium was observed for C. militaris 17944. P. tenuipes only produced stroma when it was grown on sticky rice mixed with pupal powder and on dead silkworm pupae. Growth of stroma was not observed for C. militaris.

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Embryonic development in Bombyx mori L. in three multivoltine silkworm strains, Nangnoi, Khakii and Samrong, were observed by stereo microscopy and scanning electron microscopy from day 1 after oviposition until one day before hatching. Nangnoi, Khakii and Samrong strains entered reversal stage 4 to 4.5 days after oviposition and showed ocellus, setae and spiracles on 5 to 6 days. On 7, 8 and 9 days or on 10 days, embryos were apparently observed. After head-abdominal pigmentation, the embryonic development in Khakii and Samrong strains was completed in 9 days while Nangnoi was in 10 days. In addition, SEM micrographs in Samrong strain obviously showed external morphology of the embryo.

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Two Thai multivoltine silkworms, Bombyx mori L., Nang-noi and Kotung strains and Japanese mulberry wild silkworm, Bombyx mandarina Moore were reared with fresh mulberry shoots at 25 ℃ in rearing room until measurement for cocoon weight, shell weight. Hybrid silkworm eggs were prepared from the Thai multivoltine female moths and male wild silkworm. The F1 hybrid eggs between B. mori and B. mandarina silkworms were reared with mulberry shoots. Larval duration from hatching to maturing was only 10 days which is referred as trimolter. Cocoon weight, shell weight, percentage of shell weight were superior to parental breeds. Cocoon shape was similar to that of Thai multivoltine strains, but showed in light green color instead of yellow. Fiber length, fiber weight, filament size (denier) were 406.8 ± 0.19 meters, 6.70 ± 0.11 centigrams and 1.68 ± 0.16 denier, respectively.

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Production of three colors of natural dye powder was studied by three different methods which were spray drying, freeze drying and Phthalate. The three colors were yellow color from Garcinia bark (Garcinia dulcis), Marigold (Tagetes erecta L.) and heart of jack fruit wood (Artocarpus heterophyllus); red color from lac (Laccifer lacca); and indigo color from butterfly pea (Clitoria ternatea L.). We found that the spray dry and freeze dry method can yield less in the dye production and not suitable with materials such as lac and African marigold flower because they have viscosity when compared with the carrier substances. Natural dye powder was prepared including Garcinia bark (Garcinia dulcis), Marigold (Tagetes erecta L.), heart of jack fruit wood (Artocarpus heterophyllus), Lac (Laccifer lacca) and butterfly pea (Clitoria ternatea L.) combined with mordant which consisted of salt, alum and tamarind and carrier such as white clay filler and talcum. The dye powder could be produced total in seven color tones which are grey, blue, pink, brown, red orange, and green. Comparison was made on the level with TOKA fandeck and pH value, the stability of washing and decolorizing and the test of sunlight stability. The results showed that the pH in the colors from natural materials mixed with marl is ranged from pH 6.81 to pH 9.80; that is, yellow was ranged with pH 6.90 to pH 7.71; purple with pH 7.03, blue with pH 6.70, green with pH 9.82, red with pH 7.17, and orange with pH 9.83. Meanwhile, the pH in the natural colors mixed with Talcum was ranged from pH 8.96 to pH 9.81; brown with pH 7.08 to pH 9.11, yellow with pH 6.90 to pH 7.01, purple with pH 7.03, blue with pH 6.50, red with pH 6.43, orange with pH 6.80, and pink with pH 9.73. The stability of washing and decolorizing in dying process was at good level and the test of sunlight stability also was at good and moderate levels. Most of the colors showed good resistance in exposing to the sun. It was found out that the carrier substances did not dissolve in water but the absorbed colors could be released easily. As for the substance suspended in the water used for staining, we can wash the carrier substances from silk yarn easily without interfering the fixation of the colors.

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Effect of juvenile hormone analogue (methoprene) (isopropyl (2E, 4E)-11-methoxy-3, 7, 11-trimethyl-2, 4-dodecadinoate) at concentrations of 0.003, 0.005 and 0.01ppm on Dok-Bua, Thai hybrid strain of the silkworm, Bombyx mori L, topically applied on thoracic segment, at 48, 72 and 96 hour was studied. The results showed that the mature larvae treated at 96 hr did not spin cocoons and died in the mountage. In larvae treated at 48 and 72 hour, larval duration was prolonged for two days compared with controls. Cocoon weight and cocoon shell weight increased when larvae at 48 hour were treated with 0.01 ppm methoprene. The length and the weight of fiber from treated larvae at 48 and 72 hour increased from controls.

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The objective in this preliminary study was to find the appropriate dose of Juvenile Hormone Analogue namely Pyriproxyfen to improve economic characters of Thai hybrid silkworm (Bombyx mori L.), Nanglai x J108 strain. Six doses of Pyriproxyfen (0.01, 0.05, 0.1, 0.5, 1 and 5 ppm) were applied by using the topical method on the dorsal part of the third day of the fifth instar silkworm larvae. The result showed that 0.05 ppm of pyriproxyfen was most effective on growth and economic characters and the length of larval feeding period extended 2-4 days. Consequently, cocoon weight, cocoon shell weight and pupal weight of the female increased 32.55 %, 16.58 % and 29.55 %, respectively, while those of the male increased 26.93 %, 9.03 % and 34.66 %, respectively. Cocoon weight and length of silk filament increased 3.86 and 12.86 %. However, cocoon shell ratio of both sexes decreased which indicated that pupal weight increased. The data from this experiment can be used for further studies for improving cocoon production.

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[in Japanese]

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[in Japanese]

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