Reducing agents such as glutathione and ascorbic acid inactivated a nucleopolyhedrovirus (NPV) of the silkworm in vitro. Activity of Bombyx mori NPV virions was lost after incubation with 5 mM reduced glutathione or 5 mM ascorbic acid at 25°C for 1 day. A half time of inactivation at 0.05% (2.8 mM) of ascorbic acids was estimated to be 1.5 minutes. NPV in the hemolymph from NPV-infected larvae was inactivated after treatment with 1% ascorbic acid at 25°C for 1 day. From these results, applications of ascorbic acid to disinfection against silkworm viruses were discussed.

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Through trial and error, i.c. the authors prepared a restrictive wool cloth to protect an attack by Anthrenus verbasci using dyeing techniques with natural dyestuffs. It has been found that wool clothes dyed with dyestuffs from insect orgins and natural colours derived from natural products have the restrictive potentiality against the attacking by Anthrenus verbasci, except for Lithospermum erythrorhizon and Curcuma longa. This confirms that amount of ingredients absorbed at about 280 nm, which is found in cocoons of Cricula trifenestrata, has an influence on the attack of Anthrenus verbasci on wool cloth. It is concluded that the attacking of insects is restricted by the existence of tannic acid or epicatechin. Evidence is shown by the absorption which appeared at about 280 nm. Therefore, new materials, potentiality can be prepared by using tannic acid in the dyeing procedure.

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This paper reports the application of blended yarns consisting of silk and nylon, or super hybrid silk (SHS), to produce wash-resistant silk crepes for domestic launderable kimonos. The three kinds of nylon core fibers used were semi-dull (sd), bright (br), and low-shrink (Is) nylons. Three 45/55 silk/nylon hybrid yarns (sd-SHS, br-SHS, and Is-SHS) were used to produce three different crepes (warp/weft: sd/sd-SHS, sd/br-SHS, and sd/ls-SHS). For comparison, a silk crepe and a silk-like polyester crepe were also prepared. The crepes were subjected to a series of wash and dry cycles with a household washing machine and examined for dimensional stability. The mechanical properties and six hands including stiffness (Koshi), anti-drape stiffness (Hari), crispness (Shari), fullness and softness (Fukurami), flexibility with soft feeling (Shinayakasa), and scrooping feeling (Kishimi) of the unwashed and washed crepes were measured by the KES-FB method. After five launderings, the hand value trends of the SHS crepes were similar to that of the silk crepe. They showed decreased Koshi and Hari hand values and increased Fukurami and Shinayakasa hand values. However, the changes in the hand values of the SHS crepes caused by five washings were less than those of the silk crepe. The hand values of the sd/br-SHS crepe became close to those of the polyester crepe while the sd/sd-SHS and sd/ls-SHS crepes showed similar hand values to the silk crepe. The dimensional stability and wash-and-wear properties of the SHS crepes were found to be significantly improved by using the SHS yarns. These results confirmed that the SHS crepes have excellent wash-resistance compared to the silk crepe.

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It is known that filament quality of cocoons of the silkworm reared on an artificial diet during all instars is worse than that of the silkworm raised on mulberry. To solve this problem, the polyphagous strain “TN32×TC60” was compared to the commercial strain “N124×C124” reared on two kinds of diets. Certain factors were shown to reduce the cocoon quality, for example, the filament size and shape. When the silkworms were reared on mulberry, the reelabilities of N124×C124 and TN32×TC60 were 87 and 66%, respectively. In both strains, the shape of the filaments, spinet and the water content of the silkgland were normal. When both strains were reared on an artificial diet, the reelabilities decreased and the cocoon filaments became thinner. The filament shape did not change in N124×C124, but in TN32×TC60 the shape was extremely flat although the spinet shape was normal. The anterior-middle part of the silkgland contained more water than in silkworms raised on mulberry in both strains. These results suggest that the filament size and the flat shape were factors in reducing reelability. They would be influenced by water content, and not by the shape of the spinet. We assumed that artificial diets affected the water content of liquid-silk because filament quality and water contents were improved by rearing on mul-berry only during the 5 th instar. Practically, we believe that the filament shape is suitable for the index of the polyphagous strain breeding because the flat filaments can be removed by breeding.

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