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(mayflies), an order of winged insects having two similar winged phases, the subimago and imago, which are separated by a molt. During these phases, which have a duration ranging from several seconds to several days, the insects do not feed. Some species live for only one day.
The mouthparts are vestigial, and the alimentary canal has been transformed into an air bladder. The forewings have a rich network of venation and are larger than the hind wings. Sometimes hind wings are absent. The tip of the abdomen has three segmented filaments—a pair of long, lateral cerci and one median paracercus, which is sometimes much shorter than the other two.
The mayfly undergoes incomplete metamorphosis. It has a large number of larval stages (as many as 25), and development takes place in the water for one to three years.
There are 23 widely distributed families, embracing more than 2,000 species. The USSR has 17 families, with more than 200 species. Mayflies all inhabit freshwaters, but they represent various ecological groups and have adapted to various living conditions (undergrowth, mud, rapids, soil). The larvae are food for many valuable commercial fishes, including salmon and white-fish. Ephemeropteran fossils are important in stratigraphy.
REFERENCEOpredelitel’ nasekomykh Evropeiskoi chasti SSSR, vol. 1, pages 110–36. Edited by G. Ia. Bei-Bienko. Moscow-Leningrad, 1964.
O. A. CHERNOVA