Insects in Winter - Part One

Insect are cold-blooded animals and respond to cooling temperatures in a variety of ways. Mammals can generate their own heat and have the advantage of being large. Insects are small and do not have body fat for insulation from the cold and do not produce their own heat. However, they do have several general strategies which they can employ such as or dealing with winter.  One of the most interesting means that insects use to survive winters is physiologic.

Diapause

Diapause is a suspension of development that can occur at the embryonic, larval, pupal, or adult stage, depending on the insect species. In some species, diapause is optional and occurs only when induced by environmental conditions; in other species the diapause period has become an obligatory part of the life cycle.

Some species of insects over winter in the adult stage and avoid freezing damage to their body by making a sort of biologic antifreeze material. These insects synthesize compounds such as sugars and proteins which depress the freezing point. These chemicals are called cryoprotectants, such as glycerol - similar to the stuff we pour down our sinks to prevent freezing! As temperatures increase, cryoprotectants quickly decrease. Some insects, like many plants, undergo a cold-hardening when shorter days and cooler temperatures occur. The mechanisms providing over winter cold- hardiness results from a combination of supercooling and the insect- manufactured cryoprotectants. Some Alaskan insects can survie temperature as low as  -76 degrees F.


References

Danilevskii, A. S. 1965. Photoperiodism and Seasonal Development of Insects. Oliver and Boyd, Edinburgh. 

Nijhout, H. F. 1994. Insect Hormones. Princeton University Press, Princeton. 

Tauber, M. J., Tauber, C. A., and Masaki, S. 1986. Seasonal Adaptations of Insects. Oxford University Press, Oxford. 

Web Links

Developmental Biology

Insect Winter Survival Strategies

Insect Overwintering