Life Cycle of Bombyx mori

Bombyx mori, the domesticated mulberry silkworm moth, is unisexual, about 2.5 cm long and pale creamy-white — and because its body is heavy relative to its feeble wings, the female cannot actually fly. Adults live only 2–3 days and never feed in that time: males copulate with females for roughly 2–3 hours soon after emerging (and can die shortly after if not separated), after which the female lays 400–500 eggs within 1–24 hours. Eggs come in two forms — diapause eggs, laid by temperate-region silkworms, and non-diapause eggs, laid by subtropical silkworms such as India's — and hatch after about ten days of incubation into a pale, yellowish-white caterpillar roughly 3 mm long, equipped with mandibulate mouthparts built for feeding on mulberry leaves. Over the next 21–25 days the caterpillar moults four times, passing through five larval instars, until it reaches its full length of about 7.5 cm. At that point its salivary glands take over as silk glands: the caterpillar stops feeding, secretes a sticky fluid through its spinneret (a narrow pore on the hypopharynx) that hardens into a fine silk thread on contact with air, and wraps roughly 1,000–1,200 metres of this thread — taking about 3 days to complete — around itself as a protective cocoon, whose outer threads are irregular but inner threads are neatly regular. Inside, the insect pupates for 10–12 days before cutting through the cocoon and emerging as an adult moth. Based on the number of m …