Experimental field tests of Batesian mimicry in the swallowtail butterfly .

The swallowtail butterfly is known for its striking resemblance in wing pattern to the toxic butterfly and is a focal system for the study of mimicry evolution. females are polymorphic in wing pattern, with mimetic and nonmimetic forms, while males are monomorphic and nonmimetic. Past work invokes selection for mimicry as the driving force behind wing pattern evolution in . However, the mimetic relationship between and is not well understood. In order to test the mimicry hypothesis, we constructed paper replicas of mimetic and nonmimetic and , placed them in their natural habitat, and measured bird predation on replicas. In initial trials with stationary replicas and plasticine bodies, overall predation was low and we found no differences in predation between replica types. In later trials with replicas mounted on springs and with live mealworms standing in for the butterfly's body, we found less predation on mimetic replicas compared to nonmimetic replicas, consistent with the predator avoidance benefits of mimicry. While our results are mixed, they generally lend support to the mimicry hypothesis as well as the idea that behavioral differences between the sexes contributed to the evolution of sexually dimorphic mimicry.