Flightlessness in mayflies and its relevance to hypotheses on the origin of insect flight

Abstract

Until now, only fully winged mayflies have been known. It has been proposed recently that brachyptery could be a missing link in the development of insect flight, via sailing or skimming aquatic insects. To our knowledge, we report here the first documented case of brachyptery in mayflies. The flightless genus Cheirogenesia is endemic to Madagascar, and the adults skim the water surface. This loss of the flight function has induced important physiological changes, such as a shift from lipids to carbohydrates in the energy reserves used during their adult life. Comparison of wing area of living mayflies with fossil species indicates that brachyptery could have already occurred in early flying insects (in the Permian). We argue that flight loss in Cheirogenesia has been made possible by the lack of fish predation in its natural habitats.