Cloeon dipterum is a species of mayfly that can be found in Europe, North America, and Asia, with a large population occurring near ponds in the British Isles. This species was first described by Carl Linnaeus with its current scientific name, but it has been given many other names, or synonyms, including C. pallidum, given by William Elford Leach in 1815, and C. affinis, given by Jules Pierre Rambur in 1842.
Cloeon dipterum is similar to other members of its genus in that it holds one pair of wings. The eyes of the species, known and compound eyes, show a distinct sexual dimorphism in that females hold lateral apposition eyes and males hold an extra turban-shaped dorsal eye, which is thought to allow them to see breeding females that gather in larger groups with females that are not able to breed.
Cloeon dipterum is an ovoviviparous species, which is unique among mayflies, and it is the only ovoviviparous mayfly in Europe. Ten to fourteen days after breeding, females lay their legs directly on water, after which they hatch into larvae that can survive anoxic conditions, allowing them to live even when ponds and lakes freeze over during the winter. Although the lifespan of wild individuals is unknown, captive female individuals have been known to live for up to three weeks.
Image Caption: This image shows a Mayfly of the species Cloeon dipterum. Credit: AndrÃ© Karwath/Wikipedia (CC BY-SA 2.5)