Costs and benefits of acclimation to elevated temperature in Trichogramma carverae

The consequences of acclimation for survival and other fitness components in the parasitoid wasp, Trichogramma carverae (Oatman and Pinto), were examined. Heat hardening adult wasps at 33 °C or 35 °C for one to two h increased survivorship at 40 °C. This benefit was apparent for several hours after heat-hardening and occurred in both males and females. Heat hardening at 33 °C during development also resulted in significant increases in survivorship of adults after exposure to 40 °C. However, this developmental hardening reduced longevity of adult male and female wasps and also reduced parastism rate. This suggests costs and benefits of exposure to non-lethal temperature increases. Acclimating wasps by rearing them under constant temperatures (14, 25 or 30 °C) influenced parasitism rates at these temperatures at the adult stage; only females reared at 14 °C parasitised eggs at 14 °C, while parasitism at 25 °C and 30 °C was not significantly influenced by rearing temperature. Acclimation may be useful for increasing the survival or fecundity of mass-reared Trichogramma in inundative releases, but any benefits could be offset by fitness costs of the acclimation process.