Determination of supercooling point and freezing point of Chelonus formosanus Sonan and its host

Chelonus formosanus Sonan (Hymenoptera : Braconidae) is an important parasitoid of many lepidopteran noctuid pests. It has great potential for biocontrol on these pests. In order to better understand the cold resistance of the wasp, the supercooling point and freezing point of the wasp at different developmental stages were measured and the frequency distribution was analyzed. The results showed that the supercooling points and freezing point of different developmental stages of C. formosanus were significantly different. Among them, 5-day-old pupae was the lowest, (-13.05℃), while the older larvae was the highest, (-11.08℃). The freezing point of adults was the lowest (-8.23℃), and that of older larvae was the highest (-4.25℃). The variation of supercooling point and freezing point of different individuals at different developmental stage of C. formosanus all conformed to the normal distribution. In addition, parasitism had no significant effect on the supercooling point of the host, and the supercooling point of Spodoptera litura parasitized by C. formosanus was lower than that of the unparasitized S. litura. The results showed that the cold tolerance of pupae was stronger than that of older larva and adult, and the cold tolerance of middle-aged pupae and last-instar pupae was stronger.