Common name: Mayfly
Description: Small to large in size, winged with large triangular forewings and smaller hind wings. Mouthparts are reduced. The compound eyes are large, the antennae long and filiform (sometimes multi-segmented), abdomen slender and the thorax relatively stout. There are three "tails" - paired cerci that are often as long as the median caudal appendage. The immature stages (called nymphs) are aquatic, with three "tails" and plate-like abdominal gills.
Fun facts: There are no more than a few thousand species in this small order, with the greatest diversity in temperate areas. One of the reasons that the thorax is stout is that it is enlarged for flight, the first/oldest order of insects that has flight capability. Males have enlarged forearms with which to seize the female during the mating flight. The abdomen is 10-segmented. Nymphs have anywhere between 12 to 45 aquatic instars with fully developed mandibulate mouthparts. Developing wings are visible in older nymphs. The penultimate instar or subimago (subadult) is fully winged, flying or crawling.
The subimago and adult are non-feeding and short-lived. Adults form mating swarms over water. Copulation takes place in flight and eggs are laid in water by the female.
Nymphs graze on periphyton or fine detritus; a few are predatory on other aquatic organisms. Development can take from 16 days in warm habitats to over a year in cold and high-latitude waters. Some species are multivoltine. Most nymphs occur in well-oxygenated fast-running waters.
sourced, in part, by The Insects: An outline of entomology, second ed. Gullan, P.J. and P.S. Cranston. Blackwell Science, Great Britain, 2000.