Effects of Various Temperature Regimes on the Time Required for Emergence of Diapausing Heliothis zea1,2,3,4

Diapausing Heliothis zea pupae, held at initial temperatures of 3, 8, 13, or 18°C for 7, 38, 75, or 111 days, were exposed to either 18 or 23°C until adult emergence. At 23°C, time until emergence (measured from date of transfer to 23°C) ranged from 27.5-70.0 days and was influenced by both the initial temperature and the exposure time. At 18°C most individuals had not emerged after 201 days; however, following transfer to 23°C they emerged in a mean of 20.7 days. Other diapausing pupae were held under outdoor conditions until late winter. Beginning Feb. 8, subsamples of these were transferred to 23°C at about weekly intervals. Mean days until emergence (measured from date of transfer to 23°C) was inversely related to the length of outdoor exposure and ranged from 20.9-41.4 for pupae which had not terminated diapause before transfer to 23 °C.