Temperature effects on induction of parasitization by females of Trichogramma principium (Hymenoptera, Trichogrammatidae)

The effects of temperature on induction and stability of parasitization of less preferred factitious host (the Angoumois grain moth, Sitotroga cerealella) eggs by Trichogramma principium females were studied under laboratory conditions. The percentage of parasitizing females at 15°C was significantly lower than that at 20, 25, and 30°C. At constant temperatures of 15, 20, 25, and 30°C, mean durations of pre-oviposition periods were 6.5, 2.1, 0.9, and 0.6 days, respectively (differences were significant between all regimens). In most of females, parasitization induced by high temperature (25°C) continued after the temperature decrease to 15°C. These results suggest that although emerged females are ready to lay eggs, rather prolonged pre-oviposition period may precede parasitization of less preferred hosts, and the duration of this period may depend on temperature.