The behavioural components of sexual selection in the milkweed beetle tetraopes tetraophthalmus

Body-size-specific variation in male mating success has been demonstrated in the milkweed beetle, Tetraopes tetraophthalmus by several authors. This study attempts to identify the behavioural components of this variable mating success and partition them into intrasexual and intersexual selective events. In laboratory studies, no evidence was found for an intersexual component of mate selection; neither female choice nor a variable propensity of males to mate. In both laboratory and field studies, however, male-male fighting was shown to play a large role in determining the mating success of individuals. Body-size-related variation in mating success results, in part, as a consequence of the high probability that the larger of two interacting males will deny the smaller male access to any nearby females.