Egg and larval diapause in two populations of Aedes geniculatus (Diptera: Culicidae).

Abstract

Aedes geniculatus mosquitoes diapause either as eggs (mature embryos) or as 4th- (last-) instar larvae. Photoperiod and temperature effects on induction and termination of egg and larval diapause were studied in populations from near Orgosolo, Sardinia (MTSGIOV strain), and Brighton, England (SUSSEX strain). A percentage of each population undergoes “obligate” egg diapause. In the facultative diapause portion of the population, short-day photoperiods induced diapause, while long-day photoperiods maintained egg hatchability. Warm temperatures and long days were most effective in promoting a return to hatchability among diapause eggs. MTSGIOV had a relatively weaker embryonic diapause than SUSSEX. Larval diapause was induced by short-day, cool conditions and prevented by long days in both populations. Diapause was terminated by long days. Compared to MTSGIOV, SUSSEX larvae had a longer critical photoperiod for diapause induction, stronger diapause intensity (i.e., less easily terminated), and a greater sex-related difference in intensity. Sex-related differences were present in both the induction and the intensity of egg and larval diapause. Males were less likely to enter either diapause state and had a less intense diapause than females.