Abstract: When the insect internal water changes the critical point of temperatureinto solid state, can reduce to very low extent. According to this physicalproperty, we measured the supercooling point and freezing point of hibernating and anabiotic larvae of three kinds of pine caterpillar under low temperature with semiconductor point temperature meter. We also made some lethal testswith the change of temperature at the beginning and the end of hioernationof the pests. The results are as follows:1. The supercooling points of hibernating larvae and anabiotic larvae of Dendrolimus superans are -21.89 ±0.31 and -13.18±0.39; that of D. tabulaeformis are -19.89±0.48 and -11.12±0.29; and that of D. spectabilis are-18.23±0.51, -9.14±0.27.2. The freezing points of hibernating larvae and anabiotic larvae of D. superans are -6.66±0.36 and -5.18±0.22; that of D. tabulaeformis are -6.53±0.39 and 4.61±0.21; and that of D. spectabilis are -6. 27±0.32 and-3.25±0.18. At the beginning and the end of hibernating, if the climate changesvery abruptly, then the temperature changes from 5℃--6℃ frequantly and the mortality of the overwintering larvae may be more than 90%.

Key words: Pine caterpillar, Overwintering larvae, Super-cooling point