The literature on the general subject of freezing and survival both in plants and in animals is briefly reviewed and a bibliography given. Insects representing three ecological groups, (1) the oak borers—exposed to temperature extremes normally; (2) stored‐products insects representing supposedly a tropical or subtropical group, and, (3) aquatic insects never exposed to temperatures lower than 0°C., were chosen for this study. Determinations of the freezing and undercooling points were made during the yearly cycle. Both the stored‐products insects and the aquatic insects studied showed no periodicity in freezing or undercooling. The oak borers showed marked periodicity. The freezing‐point varies directly with the moisture content. Cold‐hardiness was produced experimentally by, (1) exposure of insects to low temperatures and, (2) by dehydration. Loss of cold‐hardiness was produced experimentally by combinations of high temperature, food, and high relative humidity. The freezing‐point ordinarily found corresponds with that of the blood. Repeated freezings of the same insect or tissue showed no hysteresis. There exists in certain insects a secondary freezing‐point below that ordinarily found. Oak borers in summer condition die at the first freezing‐point; in fully hardened condition they die at the secondary freezingpoint.

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