Cold hardiness of Hypera postica

Supercooling point and freezing point in all stages and overwintering adults of Hypera postica were measured in a laboratory population. The results showed that the mean supercooling point of adult, normalwing pupae, vestigialwing pupae, 4th and 3rd instar larvae were -20.46℃, -10.34℃, -9.55℃, -10.0℃, 9.75℃, respectively while their freezing point were -18.24℃, -6.68℃, -6.52℃, -7.52℃, -7.86℃. The suppercooling point and freezing point of adult were the lowest. There were no significant differences between pupae and 3rd, 4th larvae in suppercooling point and freezing point. The difference of adults which were in different wingtype was not significant. During late December and late January, the supercooling point of female adult was lower than male adult. Thus, it revealed stronger cold hardness in adult stage than in other stages. The effect of two wing types were no significant differences, and the sex brought significant differences with the temperature decreasing.