EFFECT OF FOOD AND PERHAPS LARVAL CROWDING ON DIAPAUSE INITIATION IN TUFTED APPLE BUD MOTH (LEPIDOPTERA: TORTRICIDAE)¹

Larvae from a laboratory strain of tufted apple bud moth, Platynota idaeusali (Walker), were reared on semisynthetic diet and excised apple leaves while exposed to naturally-decreasing daylengths. Leaf-reared larvae showed a higher incidence of diapause than larvae reared on diet. The critical daylength for diapause induction in leaf- and diet-reared larvae occurred at ca. 14.8 and 14.3 h, respectively. Larvae reared on semisynthetic diet and exposed to naturally-decreasing daylengths were subjected to different levels of crowding. As the number of individuals reared together in the same container increased, the incidence of diapause increased. Separation of the effects of larval crowding from any possible effects of the quality of the semisynthetic diet on diapause induction was not attempted.