The moisture factor plays an important role in the growth, development and fecundity of insects. Rainfall can directly kill insects through mechanical scouring. Drought affects insects’ physiology both directly, and also indirectly through its effects on host plants, for example, altering interspecific interactions among insects on same host plants thereby changing the diversity and stability of the insect community and population succession. This paper summarizes the effects of rainfall and drought on the growth, development and fecundity of insects under conditions of global climate change, and provides an introduction to the behavioral responses of migratory and gregarious insects, and soil insect pests to rainfall and drought. The strategies insects use to cope with rainfall and drought are described in detail, including behavioral adaptations, and the tactics of diapause and migration etc. Artificial regulation of environmental moisture, especially soil moisture, (e.g., artificial rainfall and irrigation etc.) is suggested as a means of controlling agricultural insect pests.