Effect of high temperatures on larvae of Ephestia elutella (Lepidoptera: Pyralidae) in diapause

Diapausing larvae of Ephestia elutella (Hb.) were exposed at 40, 43 or 45°C and then transferred to 25°C to observe subsequent development and survival. All larvae died after 96 hr at 40°C, 24 hr at 43°C or 16 hr at 45°C. However, about 80% of larvae exposed to 40°C for 8 hr each day for 18 days and about 50% of larvae exposed at 43°C for 8 hr each day for seven days survived. At 45°C all larvae died after two 8-hr or three 6-hr exposures given on successive days, but eight 4-hr exposures failed to kill more than 25% of larvae exposed. When the gap between 6 and 8-hr exposures was increased from 1 day, some larvae survived, indicating that recovery from heat exposure could occur. Adults emerging after high temperature exposure of diapausing larvae proved fertile. In contrast adults from larvae pupating without diapause at 30°C are known to be infertile.

Exposures at high temperature significantly hastened the termination of diapause. In general, the higher the level of mortality in the sample, or the greater the number of exposures at high temperature, the sooner pupation occurred in long days at 25°C.