Bombyx mori breeding. Silkworm breeding is aimed at the overall improvement of silkworm from a commercial point of view. The major objectives are improving fecundity (the egg-laying capacity of a breed), the health of larvae, quantity of cocoon and silk production, and disease resistance. Healthy larvae lead to a healthy cocoon crop. Health is dependent on factors such as better pupation rate, fewer dead larvae in the mountage, shorter larval duration (shorter larval duration lessens the chance of infection) and bluish-tinged fifth-instar larvae (which are healthier than the reddish-brown ones). Quantity of cocoon and silk produced are directly related to the pupation
Bombyx mandarina differ in karyotype from those of inland China. Domestic silkmoths are closer to the latter regarding mtDNA sequence data, and especially lack some genetic apomorphies of the northeastern "B. mandarina". Thus, the initial domestic stock came from inland China. "B. mandarina" is able to hybridize with "B. mori". Both in the wild and in a domesticated environment, females release pheromones and wait for males to be attracted and fly to them. However, "B. mori" males cannot fly. Hybridisation in the wild, therefore, inevitably means breeding between domestic ("B. mori") females and wild ("B. mandarina") males. Hybridization is possible in both