Overwintering of Prepupae of Lucilia Cuprina (Diptera: Calliphoridae) in the Canberra Region

Prepupae of the Australian sheep blowfly Lucilia cuprina (Wiedemann) which entered the ground during the summer and early autumn pupated within a few days. However, through late March and early April there was a transition to almost nil pupation. Spring emergence was synchronous amongst individuals which had entered the ground from late March through to October. This suggests that prepupae which did not pupate during autumn were not accruing any developmental increments at that time, and that they were in a state of developmental arrest. Development was also frequently arrested in prepupae placed at 16°C after leaving the food source. Such arrest was markedly more frequent amongst prepupae produced between the autumn and spring equinoxes than in the rest of the year. Since prepupae were deprived of obvious seasonal cues at 16°C, it appears that the overwintering state is at least partly determined in some earlier life stage. However, prepupae placed at 25°C after leaving the food source had uninterrupted development in all seasons. The difference between the responses to 16 and 25°C suggests that temperatures experienced by prepupae themselves are also important in determining the overwintering state.