A Study on the Photoperiodic Diapause of Dendrolimus spp.

The response of photoperiodic diapause of Dendrolimus spp. varies with the larval development during its sensitive stages. The larvae have the strongest sensitivity to short photoperiods in the first instar and start to decrease in the second instar, and almost lost the sensitivity in the fourth instar. The larvae show higher sensitivity to shortday cycles in moulting stage. The longer the treatment received by larvae, the higher the ratio of diapause for the larvae in the third and fourth instars. The relationship between the photoperiodic reaction and the content of juvenile hormone is discussed.