During a period of controlled, highly fluctuating daily Temperatures., oviposition of the eastern strain of Hypera postica (Gyllenhal) changed rapidly in response to the temperature. The number of ovipositing females, the total number of eggs deposited, and the average number of eggs per ovipositing female per 24-hour period all increased significantly as the temperature was increased from 5° to 35°C. The presence of a male with a female in a petri dish significantly reduced the female’s reproductive rate at 24±1.5°C. The average number of eggs per female, the total number of eggs per group of females, and the percentage of females ovipositing were greater in isolated, multiple-mated females than in individual females confined with a male.