Abstract

Many studies have demonstrated that many species of parasitoid wasps can control offspring sex ratio in response to environmental variables. This article tests the effects of temperature, relative humidity, photoperiod, foundress number, foundress age, host number, interval time of host supplying, species of food, species of host and symbiotic bacterium (Wolbachia) on sex ratio of Trichogramma ostriniae. Results showed that the sex ratio of T. ostriniae was affected significantly by temperature (35°C), number of foundress (>2 number), age of foundress (3-day-old) and Wolbachia. Through transmitted Wolbachia from Trichogramma embryophagum to Trichogramma dendrolimi, even the reproductive mode of T. dendrolimi was changed from gamogenesis to thelytoky. Our work verifies the sex ratio theory and implies that the potential effectiveness ofTrichogramma spp. as a biological control agent can be further improved.

Key words: Environmental factors, biological factors, sex ratio, Wolbachia, Trichogramma ostriniae.