Role of photoperiod, temperature, and injury in induction and termination of the pupal diapause of Heliothis zea (Boddie)

Abstract

Investigations were conducted on bollworms, Heliothis zea (Boddie), reared on artificial diet under environmentally controlled conditions to determine the influence of photoperiod and temperature on the induction of pupal diapause. In addition, the seasonal incidence of diapause and the process of diapause termination were studied under natural and laboratory controlled conditions. The adult, egg, and larval stages of the bollworm were found to be sensitive to photoperiod, and each stage had to be subjected to daylengths within a relatively specific range before diapause could be induced in the pupal stage. To obtain a high incidence of diapause, both adults and eggs had to be subjected to daylengths of 11 hours or longer and the larvae to daylengths of less than 13 hours. The maximum incidence of diapause occurred when the adults or adults and eggs were held in a 12 hour day while the eggs and larvae or larvae only were held in an 11 hour day. When other daylengths were employed, both the adults and eggs had to experience a longer daylength than the larvae before a high incidence of diapause occurred. The seasonal incidence of diapause occurred at approximately the same time during 1965 and 1966, and was found to be correlated with a decreasing daylength from 13 to 12 hours. The subsequent maximum incidence of diapause among the insectary population occurred during the period when the daylength decreased from approximately 12.5 to 11.5 hours. This was in agreement with the results obtained from previous studies at this laboratory. ...