Rearing of a commercial silkworm variety “Kinshu × Showa” on an artificial diet throughout the all larval stage

The most popular commercial silkworm variety in Japan is “Kinshu × Showa”. This variety is now utilized for production of pharmaceutical supplies including medicine by rearing larvae on artificial diets. Hence the parameters such as consumption of diet and growth rate of larvae, and consumption of diet and cocoon characters such as cocoon weight, cocoon shell weight, cocoon shell ratio, and pupal weight in the rearing on an artificial diet should be very useful to improve the productivity of the products. This study was carried out to clarify the parameters for this variety. The silkworm larvae were reared on the artificial diet “Silkmate 2S”, produced by Nosan Corporation, Yokohama, Japan. It is known that the amount of diet eaten by the silkworms during the fifth larval instar affects the health of them. The relation between the amounts (12, 13, 14g / individual) and the rearing performance of the variety was investigated. On the second day of fourth instar the larvae were counted and retained 300 larvae in each treatment. Silkworms developed healthy and did not die until mounting stage. The pupation rate decreased according to the increase of the amount, i.e. 97.3%:12g, 96.3%:13g, 94.7%:14g. Cocoon weights and cocoon shell weights increased according to the amount, i.e. 1.71g 33.8cg:12g, 1.81g 35.5cg:13g, 1.85g 37.6cg:14g. The shell ratio was almost same and the value was 19.6～20.3%. The quantity of products based on the number of larvae at the start of the treatment were compared. The 14g was maximum on cocoon and cocoon shell. The values were 175.2g / 100 individuals and 35.6g / 100 individuals respectively. On the production of pupal body, the 13g and the 14g were the same and the value was 139.5g / 100 individuals. Three hundred and ninety-eight silkworms were brushed and reared without the adjusting of number at the fourth instar, 389 silkworms (97.8% of the brushed silkworms) matured for spinning at the mounting stage and only 2 silkworms stayed immature. From the above results the adjusting of silkworm number at the fourth instar is not required for the artificial diet rearing of this variety. The reeling performance of the cocoons obtained through the experiments was investigated. As the comparative control, some silkworms with the same origin as the silkworms reared on the artificial diet were reared on the same artificial diet during first to third instar and on mulberry leaves during fourth and fifth instar, and let them spin in the same spinning room. The filaments of the cocoons made by the silkworms reared on the artificial diet were thicker and shorter than that of the silkworms reared on mulberry leaves during fourth and fifth instars. On the reelability, difference was not found between them.