Courtship in long-legged flies (Diptera: Dolichopodidae): function and evolution of signals

Analyzing the courtship behavior of long-legged flies (Diptera: Dolichopodidae), we focus on the evolutionary development of courtship signals. Long-legged flies may serve as a model for this evolutionary process, because males of some species present sexually dimorphic badges during courtship, whereas others do not exhibit such conspicuous signals but present lavish courtship behavior, including dynamic flight maneuvers. A comparison of these two groups within a single taxonomic family provides insight into the evolution of courtship signals and the corresponding behavior. Males of the closely related Empididae do not possess such badges. Within the super-family Empidoidea, we propose an evolutionary shift from dynamically courting and mating on the wing (in Empididae) to courting and mating on ground (in Dolichopodidae), accompanied by signaling through badge-waving. By comparing previously published data and observations on courtship behavior in Dolichopodidae, we present the hypothesis that the latter replaced the former energetically expensive behavior as a case of automimicry and sensory trap.