Insect diapause is a delay in development evolved in response to regulatory recurring periods of adverse environmental condition. Diapause has evolved in most insect species to ensure survival under unfavorable environmental conditions and to syncronize of the growth rate of the population. It is not referable to immediately prevailing adverse environmental condition, and thus differs from a delay produced by currently adverse conditions such as low temperatures. This paper was mainly based on the study of Denlinger.