Diapause induction and termination in the parasitoid Colpoclypeus florus (Hymenoptera : Eulophidae): Role of photoperiod and temperature

The processes involved in the induction and termination of facultative larv al diapause in the parasitoid Colpoclypeus florus (Walker) was investigated in the laboratory. Larval diapause in C. florus is under maternal control. Photoperiod is the major factor governing the induction of larval diapause in C. florus. The pupa of the maternal generation is the most sensitive st age though the adult is also sensitive. Adult sensitivity increases with ag e, in particular at low temperatures. Photoperiod has no effect on the deve loping larva. The critical photoperiod for diapause induction for parasitoi ds maintained throughout the life cycle at 15 and 20 degrees C was found to be 15 and 13.5 h, respectively. No diapause was induced at 25 degrees C at any photoperiod examined. A chilling period of >5 wk is a prerequisite for diapause termination. After 8 wk at 5 degrees C, all diapausing larvae pup ate within 20 d whether held under short or long daylength. Chilling temper ature and duration of chilling significantly affected diapause termination. Diapause development proceeds rapidly as chilling period increases and tem perature decreases. The role of diapause in the biology of this parasitoid is discussed.