[The influence of diurnally alternating temperatures on the pink bollworm Pectinophora : I. Duration of development, larval body weight amd fecundity]

Abstract

The temperature dependence of developmental time, larval body weight and fecundity of Pectinophora gossypiella was determined in 6 constant temperatures between 14°C and 34°C and 5 diurnally alternating temperature conditions, which had a nearly rectangular profile and an amplitude of 8°C.In the measured temperature range no differences in the developmental time were found between constant and alternating temperatures. Both, the duration of embryonic development and the generation time of animals reared in alternation conditions, were in accordance with the values of the mean constant temperatures. Alternating temperatures, however, advanced the increase of larval body weight and stimulated oviposition. The number of eggs per female was nearly twice the number as compared with the corresponding constant temperature. The conditions for maximum fecundity were alternating temperatures around 26°C.Additionally important effects of diurnally alternating temperatures, which may become effective for population increase also under field conditions, were an extended temperature range for oviposition, less egg mortality and an increase of larval diapause induction in alternating temperatures with low night temperatures.