Abstract
The larvae of the oriental fruit fly did not show any diel rhythmicity in the jumping behavior under continuous darkness or light at 20 and 25°C. When the larvae were reared under 12L:12D, they jumped out at around the time of light-on, under 6L:18D during the dark period, and under 18L:6D during the light period. When the larvae were transferred to continuous darkness from 12L:12D cycles at 25°C, they jumped out at about 24hr intervals, but the rhythmicity disappeared in continuous light. When they were exposed to a thermoperiod (25°C:20°C), the jumping activity was most pronounced immediately after the temperature drop. When they were kept at constant temperatures after thermoperiodic treatments, the diel jumping rhythm was maintained at 20°C, but not at 25°C. In order to respond to the light-on stimulus, they seemed to require several hours of preceding dark period. A much shorter period of high temperature was necessary to elicit them the jumping behavior in response to a temperature drop. By transferring the larvae reared in temperature cycles from darkness to light, it was found that the light-on stimulus effectively induced the jumping activity only in the low temperature period.
