Review of the genera of Mayflies of Panama, with a checklist of Panamanian and Costa Rican species (Ephemeroptera)

Abstract

Abstract The ancient insect order of Ephemeroptera, or mayflies, is a major component of the invertebrate fauna of freshwater habitats. They are found in lakes, ponds, and streams on all continents except Antarctica, as well as on many islands. The aquatic immature stages, or nymphs, play an important role in freshwater ecosystems by feeding on detritus and algae, and by serving as prey for fish and other aquatic animals. Adults are short-lived and frequently swarm at dusk or dawn. During swarming activities they are preyed upon heavily by dragonflies, birds, and bats. Although the importance of mayflies in temperate stream ecology is well documented, a relative lack of studies on tropical aquatic insects has meant that the importance of mayflies in tropical streams has sometimes been under-appreciated. Almost 5 months of field work in Panama (and many more in the United States) have convinced me that Panamanian and North American mayflies have comparable importance in their respective aquatic ecosystems. Figure 4.1 is a diagram of a mayfly adult, or imago, illustrating morphological terms used in this and other taxonomic papers. The genus depicted is North American but the terms apply generally. A nymph of the same genus is shown in Figs 4.2 and 4.3, also labelled. The life cycle of mayflies contains a flying but sexually immature subadult stage called a subimago which is unique to the Ephemeroptera. After a short time, usually within a day, the subimago moults to the fully mature adult or imago stage. Subimagos closely resemble imagos in appearance but can be distinguished by the cloudy appearance of their wings, the presence of a fringe of hair on the hind margins of the wings and, in males, the undeveloped condition of the genitalia. (In a few groups, the female never moults to the imago but completes her reproductive activities as a subimago.) Because the taxonomy of adult mayflies depends heavily on the structure of the male genitalia, female imagos and subimagos of either sex frequently cannot be identified. Nymphs can be identified most reliably when they are mature (almost ready to moult to the subimago stage) but generic identifications can usually be made on nymphs that are half grown or older.