Studies on Multiple Crossing of Some Popular Cross Breeds of Bombyx mori L. in West Bengal

Of all factors that govern productivity in sericulture, the role of silkworm egg is of prime importance. It is the sheet anchor of sericulture industry. Timely supply of appropriate quality and adequate quantity of disease free silkworm eggs to the sericulturists is crucial for successful harvest of cocoon crops. Silk moths have a tendency to pair immediately after emergence from cocoons. The present study indicates that in case of N×M₁₂W, N×NB₄D₂ and N×YB crossbreeds at least 95%-99% fertilized eggs can be procured by using a single male moth for 4 times in crossing. So, if male moths are used 4 times during multiple crossing it would not affect the fertility of eggs. The present investigation also reveals that total fecundity almost remained same with control when male moths were even used for seven times in crossing. This suggests that that a single male moth can be used for four times by giving them sufficient rest in crossing with female moth and in this way a grainure can save considerable cost and hazards during the purchasing of seed cocoons of male components.