Migration is a behavioral strategy that allows insects to respond to seasonal changes in resources and the environment. Insects not only escape adverse environmental conditions through migration, but their exceedingly high fecundity allows them to rapidly increase their population size on arrival in favorable new habitats, causing outbreaks that have a severe effect on both natural and agricultural ecosystems. Based on the concept of partial migration, this article firstly describes the differences in morphology, behavior, and physiology between migratory and resident insects, focusing on the relationship between migration and concomitant reproduction, as well as external environmental factors that induce migration. Finally, the authors review and summarize the progress in research on the molecular mechanisms regulating insect migratory behavior. From sensing adverse environmental signals to deciding to migrate, from take-off, flying and landing, to deciding to continue or terminate migration, the whole process largely depends on important internal factors, including endocrine and epigenetic regulatory factors. The underlying molecular mechanisms, however, require further investigation.