Oviposition in DDT-resistant and susceptible strains of Aedes aegypti (L.): time from blood-meal to oviposition

Abstract

Oviposition time (the time from blood-meal to egg deposition) has been investigated in five strains of Aedes aegypti (L.), two being DDT-resistant (from Trinidad and Haiti) and three susceptible (from West Africa (2) and Haiti). All the strains except the two DDT-resistant ones differed significantly from one another in mean oviposition time.There was a close correlation between mean oviposition time, oviposition period (the over-all period during which eggs are laid) and ‘oviposition light preference’, both the former being greater in the ‘dark-laying’ strains than in the ‘light-laying’ ones. There was a positive correlation amongst four of the strains between degree of DDT-resistance and both mean oviposition time and oviposition period; the fifth, which combined long oviposition time with susceptibility to DDT, was a recently colonised West African strain.In small mass crosses between two strains differing markedly in mean oviposition time, this character showed no dominance; it appears to be under poly genie control. Evidence is given which indicates that there is no close genetic connection between oviposition time and DDT-resistance. There is also no obvious genetic association between oviposition time and ‘oviposition light preference’.It is concluded that the observed differences in oviposition time may have come about as a result of DDT selection, but could equally well have been the result of a selective influence exercised by the laboratory environment.