Transformer-2 (Tra-2) gene plays a key role in the regulatory hierarchy of sexual differentiation in somatic tissues and in the germline of Drosophila melanogaster. Sex-lethal (Sxl) plays a complicated and important role in embryogenesis, metamorphosis, somatic sexual development, and sex differentiation in insects and its highest expression levels were observed in testis and hepatopancreas [32, 33]. In our transcriptome database, we identified four Tra-2 isoforms designated as Estra-2a, Estra-2b, Estra-2c, and Estra-2d. Together with sex-lethal (Sxl) and double sex (dsx), most of ortholog genes in “Sxl-Tra/Tra-2-Dsx/Fru” pathway are detected. In the process of male differentiation, the expression of IAG and Tra-2 was significantly upregulated (Table 2), whereas the expression change of Sxl and Dsx was not significant, which illustrated that IAG and Tra-2 may play a more important role in promoting the development of testis and stimulating male related behaviors.