The smell of attraction; cuticular hydrocarbon (CHC) profiles in a horned beetle

The Asian Rhino beetle, Trypoxylus dichotomus, is characterized by its large pitchfork horns on the heads of males. They use these horns to battle each other for access to limited females and are thought to only engage in male competition. However, recent field studies suggest that females may be choosy, selecting male mates based on traits other than the horns. In many insects, cuticular hydrocarbons are used by females to choose attractive, high quality males as mates. In particular, nutrition and stress are known to affect the blends of hydrocarbons found on the surface of the exoskeleton, and as a result females can use hydrocarbon profiles to pick good conditioned males. In order to test whether cuticular hydrocarbons might be functioning this way in Rhino beetles, I am conducting the first ever quantification of CHC profiles in this species. During Summer 2018, I collected CHC samples from 40 male beetles spanning a range of body sizes and conditions during their lives. Using the UM chemistry department facilities, I am testing for correlations between CHC profiles, static condition (body size), and dynamic condition (body weight) of male T. dichotomus. My results will help reveal a surprising aspect of the sexual behavior and mating system of this charismatic and widespread beetle