"Nonadaptive" Hilltopping Behavior in Male Checkerspot Butterflies (Euphydryas editha)

Abstract

A fluorescent-dye technique permitted the mating success of male checkerspot butterflies aggregating on a ridge to be compared with that of males on the slope below. Unexpectedly, the males on the ridge had about one-half the mating success of those on the slope. We suggest that formation of this and some other hilltopping aggregations is a "nonadaptive" consequence of otherwise adaptive behavior.