Abstract: Therm hysteresis found at first in insects, is one of the basic characteristics of antifreeze proteins (AFPs). Comparing with fish and plant AFPs, the insect AFPs has higher therm hysteresis activityand unique chemical structure features. It plays an important role in the physiological antifreeze course ofinsects, as follows: 1) inhibiting the growth of ice crystals; 2) increasing freeze-tolerance; 3) possiblycontributing to water balance of insects. Photoperiod, temperature and humidity are the external factorsthat regulate the metabolism of AFPs; and the changes of hormone in the body may be the direct internalcauses that control the AFPs' synthesis in the fat body.

Key words: insects, antifreeze proteins, therm hysteresis activity