Abstract:  The sterile insect technique (SIT) has been used for decades to control agricultural and human health-related insect pests. Compared with insecticide control strategies, SIT has several attractive features including species-specificity and environmental friendliness. A major obstacle for SIT approach that involves the release of sterile males is the separation of males from females during the mass rearing stage in order to improve the cost-efficiency of these methods and to prevent the release of biting and disease-vectoring females. In most current genetic control programs targeting dipteran insects, sex separation is not used. Currently sex separation for a small number of dipteran insects is manually and mechanically achieved based on the pupal size or the difference in the eclosion time between female and male pupae. The molecular mechanism of sex determination and differentiation in dipteran insects varies, and exploration of the primary signal has revealed major differences. Several sex determination genes have been explored in the sex separation system. The sex ratio distortion strategy produces male-biased populations by disrupting the expression of the key genes in sex-determination pathway, and the conditional female death strategy achieves sex separation by using the sex-specific alternative splicing of the key genes in sex-determination pathway. Both of these two sex separation strategies are currently under evaluation for mass-rearing program in SIT. Differences in sexual dimorphism and genetic markers between females and males have been successfully employed in the visual separation strategy for dipteran insects. We reviewed the recent advances in sex ratio distortion, conditional female death strategy and visual separation strategy in dipteran insects. We assessed with emphasis the suitability of these methods in large-scale rearing of males for mass release in order to achieve more breakthroughs in the research of pest control based on the better sex-separation techniques.

Key words: Diptera, sex determination, sex separation, sexual dimorphism, sterile insect technique, transgenic technology