Distinct developmental mechanisms influence sexual dimorphisms in the milkweed bug .

Sexual dimorphism is common in animals. The most complete model of sex determination comes from , where the relative dosage of autosomes and X chromosomes leads indirectly to sex-specific transcripts of (). Female Dsx interacts with a mediator complex protein encoded by () to activate female development. In males, the transcription factor encoded by () promotes male-specific behaviour. The genetics of sex determination have been examined in a small number of other insects, yet several questions remain about the plesiomorphic state. Is required for female and male development? Is conserved in male behaviour or morphology? Are other components such as functionally conserved? To address these questions, we report expression and functional tests of , and in the hemipteran , characterizing three sexual dimorphisms. prevents phenotypes in all sexes and dimorphic traits in the milkweed bug. and are expressed across the body, in females and males. and also affect the genitalia of both sexes, but have effects limited to different dimorphic structures in different sexes. These results reveal roles for and distinct from other insects, and demonstrate distinct development mechanisms in different sexually dimorphic structures.