Bombyx mori silk only once annually. The second type is called bivoltine and is normally found in China, Japan, and Korea. The breeding process of this type takes place twice annually, a feat made possible through the slightly warmer climates and the resulting two life cycles. The polyvoltine type of mulberry silkworm can only be found in the tropics. The eggs are laid by female moths and hatch within nine to 12 days, so the resulting type can have up to eight separate life cycles throughout the year. Eggs take about 14 days to hatch into larvae, which eat continuously. They have
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