2 - Which Seasons Are Being Avoided?

Summary

This chapter identifies seasons that are avoided by entry into diapause. The best documented studies on diapause examine overwintering in temperate latitudes. Most overwintering insects enter diapause in early autumn in response to the shortening daylengths that reliably foretell the advent of winter. But summer diapauses are also quite common, especially as a mechanism for synchronizing activity with seasonally restricted food sources. Daylength may regulate summer diapause, but instead of short days, the long days of early summer frequently are used to program such a diapause. Diapause is also widespread among tropical species, especially for bridging dry seasons. Near the equator, the role of daylength may be replaced by cues provided by host plants, moisture levels, or temperature changes. Insects living at high latitudes also rely on diapause, but the fact that multiple years may be required to complete development means that diapause may intercede several times during the life cycle.