Certain Factors Influencing Diapause in the Pink Bollworm, Pectinophora gossypiella1

Abstract

Larvae of the pink bollworm ( Pectinophora gossypiella (Saund.)) reared on certain artificial diets were exposed to various environmental conditions in order to study the influence of these factors on the incidence of diapause. Regardless of the diet, exposure to temperatures of 70° F. or lower was sufficient to cause diapause in a high percentage of the larvae tested. The longer the exposure period the greater the percentage of diapausing larvae. A high incidence of diapause occurred when larvae reared on cottonseed meal diets were exposed to either short or abnormally long days. Diapause did not occur with exposure to a typical long day of 14 hours of light. Under these photoperiodic conditions, a greater percentage of diapausing larvae was observed among individuals reared on a 5% oil diet than on one containing 1% oil. No response to photoperiod was obtained in larvae reared on a wheat germ medium. These results indicate that a probable relationship exists between photoperiodism and diet as factors inducing diapause in the pink bollworm. Relative humidity was also found to influence the incidence of diapause in larvae produced on the cottonseed meal diets.