Photoperiod and temperature as factors controlling the diapause of the sunflower moth, Homoeosoma electellum

Abstract

Induction of larval diapause of the sunflower moth, Homoeosoma electellum (Hulst), was found to be dependent upon both temperature and photoperiod. Diapause was induced more readily at 21 than at 27°C, but only in photoperiods having 11 hr or less of light/day. Greatest percentages of diapausing larvae occurred among larvae subjected to 10 hr or less light time/day at 21°C, regardless of the photoperiodic exposure of the parents and eggs. The incidence of diapause was extremely low when larvae were subjected to periodic reductions in either temperature or day-length. A concomitant reduction of temperature and day-length increased the percentage of diapausing larvae to some degree, but this was small compared to percentages obtained among larvae maintained in days of 11 hr or less at 21°C. Diapause termination may be influenced by temperature and photoperiod. Diapause termination required less time at 27° than 21°C. Also, larvae which were subjected to photoperiods having 11 hr or more light/day resumed development more rapidly than larvae held in shorter light periods.