Abstract: Clarifying insect sex determination mechanisms can lay a strong theoretical basis for sex-ratio manipulation, and can also help us to develop new ways for effective pest control. Insects have evolved a bewildering diversity of mechanisms to generate the two sexes. However, the sexual development of an insect is mainly defined through a hierarchical control of several sex determining genes. This article summarized the recent studies and progress in sex determination mechanisms in model insects, focusing on genes and their cascade interactions involved in sex determination. Previous studies have demonstrated that the important sex determination genes are mainly located on autosome, and some of them have close cascade interactions, such as Sxl, tra,dsx, csd, fem, etc. Among these genes, tra and  dsx are functionally conserved, and tra regulates the transcription of the downstream gene—dsx through sex-specific alternative splicing. The tra/fem→dsx mode of sex determination is prevalent in most studied insects. Although sex determination mechanisms in most insects remain largely unclear, the study of sex determination mechanisms in some model insects has achieved great progress in recent years. Moreover, the mechanism study of sex determination in nonmodel insects has attracted extensive attention though it is still in its infancy stage.

Key words: Insects, sex determination mechanism, hierarchical regulation; , transformer gene, doublesex gene, alternative splicing