Abstract:Trichogramma dendrolimi (Hymenoptera: Trichogrammatidae) has been successfully produced in fresh caesarean-birth eggs of Chinese tussah silkworm, Antheraea pernyi, and widely used in biological control of important pests in China. To avoid the loss in production caused by unwanted diapause and develop technology for long-term storage of the parasitoid, we investigated the diapause rates of T. dendrolimi in caesarean-birth eggs of Antheraea pernyi under 10 alternating temperature regimes, i.e. 16-1℃, 16-4℃, 16-7℃, 16-10℃, 13-1℃, 13-4℃, 13-7℃, 10-1℃, 10-4℃ and 7-1℃ combined with 9 different exposure times, i.e. 13, 16, 19, 22, 25, 28, 31, 34 and 37 days at each of temperature regimes. A temperature regime of 16℃ for 10 hours and 1℃ for 14 hours each day is indicated by "16-1℃". The results from the experiments indicated that temperature, exposure time and their interactions had a significant influence on diapause rates of the parasitoids. 13-7℃, 13-1℃ and 13-4℃ were the optimum temperature to induce T. dendrolimi into diapause. 16-1℃,16-4℃,16-4℃,10-1℃ and 10-4℃ had moderate effect on the diapause induction. While 16-10℃, 16-7℃ and 1-7℃ were not effective temperatures for diapause induction. Under effective alternating temperature regimes, the diapause rate increased as exposure time increased. However, when exposure time increased to more than 28 days, diapause rate did not increase significantly with exposure time. Sigmoid models were developed to describe relationships between diapause rate and exposure time at 10-1℃, 10-4℃, 13-1℃, 13-4℃ and 13-7℃, respectively. High diapause rates, e.g. 60%-70%, were obtained by inducing at 13-7℃ for over 28 days.