Factors affecting adult diapause initiation in the tropical butterfly Hypolimnas bolina L. (Lepidoptera: Nymphalidae)

The mechanism responsible for initiation of reproductive diapause was explored in a population of the butterfly Hypolimnas bolina from the Australian wet/dry tropics. Diapause occurred independently of temperature, and was initiated in females when larvae were reared under a short day photoperiod only (12 : 12 h). The dormancy status of males was unresolved, with sperm present throughout the year, a strategy that may enable them to take advantage of unpredictable female activity. The diapause response in females was modified by the weight of developing larvae, with pupae below a critical weight threshold (0.72 g) failing to enter diapause as adults, regardless of the photoperiod experienced during development. Even above the weight threshold, 100% diapause did not occur, with a small number of females (18%) developing directly, regardless of weight and photoperiod. This facultative diapause strategy may allow individual females to take advantage of the unpredictable timing of tropical seasons