Cholesterol cycle during development of normal and nonspinning Bombyx moriL. (Lep., Bombycidae) larvae

Cholesterol content of Bombyx mori larvae was measured in two different sil kworm groups, normally spinning and nonspinning, respectively. Cholesterol content in the spinning group showed very high values immediately after the moults, following which the concentration decreased and reached a minimum before the next moult. Alternatively, cholesterol content in the nonspinnin g group during the fifth instar increased up to the death of the larvae. Co mparable behaviour was observed in a small percentage (about 20%) of nonspi nning larvae of the second group. The reason for the nonspinning behaviour is not clear.