Aggregation is a common phenomenon in the animal kingdom, particularly among insects. The reasons why insects aggregate are complex and varied. Most scholars attribute aggregation to environmental heterogeneity, communication, and interaction between conspecific individuals. Few studies have delved into the internal mechanism of communication and interaction, with most focusing on the transmission and recognition of chemical signals. There has been significant progress in research on insect aggregation over the past two decades. This review provides a comprehensive summary of domestic and international research on insect aggregation since the 1970’s. It covers various aspects of aggregation behavior, including patterns, mechanisms, functions, significance and adaptive evolution. It is, therefore, as a valuable resource for future research on insect aggregation.