The Effect of Photoperiod on Diapause Induction in Aedes canadensis and Psorophora ferox (Diptera: Culicidae)1

Abstract

The effect of various artificially produced photoperiods on diapause induction in Aedes canadensis (Theobald) and Psorophora ferox (Humboldt) was studied in the laboratory. A. canadensis eggs subjected to a daily regime of 9 h of photophase and 15 h of scotophase for the 1st 14 days after oviposition did not hatch. The critical daily photoperiod for A. canadensis was between L:D 13:11 and L:D 14:10 (h photophase:scotophase per 24 h period). Short daily photophases during the 1st 14 days after oviposition did not induce diapause in P. ferox eggs. When all life cycle stages of the parental generation of P. ferox were subjected to short daily photophases, however, there was a marked reduction in the hatch rate of eggs of the subsequent generation. In contrast to A. canadensis , 100% of incidence of diapause was not produced in P. ferox . The greatest incidence resulted in the latter species when both the entire parental generation and embryonating eggs of the F1 generation were exposed to short daily photophases.