Су құбылыстары: Эфемероптера тобының жәндіктері

Aquatic insects of the order Ephemeroptera

Mayflies (also known as shadflies or fishflies in Canada and the upper Midwestern United States, as Canadian soldiers in the American Great Lakes region, and as up winged flies in the United Kingdom) are aquatic insects belonging to the order Ephemeroptera. This order is part of an ancient group of insects termed the Palaeoptera, which also contains dragonflies and damselflies. Over 3,000 species of mayfly are known worldwide, grouped into over 400 genera in 42 families. Mayflies have ancestral traits that were probably present in the first flying insects, such as long tails and wings that do not fold flat over the abdomen. Their immature stages are aquatic fresh water forms (called "naiads" or "nymphs"), whose presence indicates a clean, unpolluted and highly oxygenated aquatic environment. They are unique among insect orders in having a fully winged terrestrial preadult stage, the subimago, which moults into a sexually mature adult, the imago. Mayflies "hatch" (emerge as adults) from spring to autumn, not necessarily in May, in enormous numbers. Some hatches attract tourists. Fly fishermen make use of mayfly hatches by choosing artificial fishing flies that resemble them. One of the most famous English mayflies is Rhithrogena germanica, the fisherman's "March brown mayfly". >

The final moult of the nymph is not to the full adult form, but to a winged stage called a subimago that physically resembles the adult, but which is usually sexually immature and duller in colour. The subimago, or dun, often has partially cloudy wings fringed with minute hairs known as microtrichia; its eyes, legs and genitalia are not fully developed. Females of some mayflies (subfamily Palingeniinae) do not moult from a subimago state into an adult stage and are sexually mature while appearing like a subimago with microtrichia on the wing membrane. Oligoneuriine mayflies form another exception in retaining microtrichia on their wings but not on their bodies. Subimagos are generally poor fliers, have shorter appendages, and typically lack the colour patterns used to attract mates. In males of Ephoron leukon, the subimagos have forelegs that are short and compressed, with accordion like folds, and expands to more than double its length after moulting. After a period, usually lasting one or two days but in some species only a few minutes, the subimago moults to the full adult form, making mayflies the only insects where a winged form undergoes a further moult.

Adult mayflies, or imagos, are relatively primitive in structure, exhibiting traits that were probably present in the first flying insects. These include long tails and wings that do not fold flat over the abdomen. Mayflies are delicate looking insects with one or two pairs of membranous, triangular wings, which are extensively covered with veins. At rest, the wings are held upright, like those of a butterfly. The hind wings are much smaller than the forewings and may be vestigial or absent. The second segment of the thorax, which bears the forewings, is enlarged to hold the main flight muscles. Adults have short, flexible antennae, large compound eyes, three ocelli and non functional mouthparts. In most species, the males' eyes are large and the front legs unusually long, for use in locating and grasping females during the mid air mating. In the males of some families, there are two large cylindrical "turban" eyes (also known as turbanate or turbinate eyes) that face upwards in addition to the lateral eyes. They are capable of detecting ultraviolet light and are thought to be used during courtship to detect females flying above them. In some species all the legs are functionless, apart from the front pair in males. The abdomen is long and roughly cylindrical, with ten segments and two or three long cerci (tail like appendages) at the tip. Like Entognatha, Archaeognatha and Zygentoma, the spiracles on the abdomen don't have closing muscles. Uniquely among insects, mayflies possess paired genitalia, with the male having two aedeagi (penis like organs) and the female two gonopores (sexual openings). this last but one winged (alate) instar usually lives a very short time and is known as a subimago, or to fly fishermen as a dun. Mayflies at the subimago stage are a favourite food of many fish, and many fishing flies are modelled to resemble them. The subimago stage does not survive for long, rarely for more than 24 hours. In some species, it may last for just a few minutes, while the mayflies in the family Palingeniidae have sexually mature subimagos and no true adult form at all. The lifespan of an adult mayfly is very short, varying with the species. The primary function of the adult is reproduction; adults do not feed and have only vestigial mouthparts, while their digestive systems are filled with air. Male adults may patrol individually, but most congregate in swarms a few metres above water with clear open sky above it, and perform a nuptial or courtship dance. Each insect has a characteristic up and down pattern of movement; strong wingbeats propel it upwards and forwards with the tail sloping down; when it stops moving its wings, it falls passively with the abdomen tilted upwards. Females fly into these swarms, and mating takes place in the air. A rising male clasps the thorax of a female from below using his front legs bent upwards, and inseminates her. Copulation may last just a few seconds, but occasionally a pair remains in tandem and flutters to the ground. Males may spend the night in vegetation and return to their dance the following day. Although they do not feed, some briefly touch the surface to drink a little water before flying off. The larval growth rate is also temperature dependent, as is the number of moults. At anywhere between ten and fifty, these post embryonic moults are more numerous in mayflies than in most other insect orders. The nymphal stage of mayflies may last from several months to several years, depending on species and environmental conditions. When ready to emerge, several different strategies are used. In some species, the transformation of the nymph occurs underwater and the subimago swims to the surface and launches itself into the air.

Nymphs live primarily in streams under rocks, in decaying vegetation or in sediments. Few species live in lakes, but they are among the most prolific. For example, the emergence of one species of Hexagenia was recorded on Doppler weather radar by the shoreline of Lake Erie in 2003. In the nymphs of most mayfly species, the paddle like gills do not function as respiratory surfaces because sufficient oxygen is absorbed through the integument, instead serving to create a respiratory current. However, in low oxygen environments such as the mud at the bottom of ponds in which Ephemera vulgata burrows, the filamentous gills act as true accessory respiratory organs and are used in gaseous exchange. In most species, the nymphs are herbivores or detritivores, feeding on algae, diatoms or detritus, but in a few species, they are predators of chironomid and other small insect larvae and nymphs. Nymphs of Povilla burrow into submerged wood and can be a problem for boat owners in Asia. Some are able to shift from one feeding group to another as they grow, thus enabling them to utilise a variety of food resources. They process a great quantity of organic matter as nymphs and transfer a lot of phosphates and nitrates to terrestrial environments when they emerge from the water, thus helping to remove pollutants from aqueous systems. The nymphs are eaten by a wide range of predators and form an important part of the aquatic food chain. Fish are among the main predators, picking nymphs off the bottom or ingesting them in the water column, and feeding on emerging nymphs and adults on the water surface. Carnivorous stonefly, caddisfly, alderfly and dragonfly larvae feed on bottom dwelling mayfly nymphs, as do aquatic beetles, leeches, crayfish and amphibians. Besides the direct mortality caused by these predators, the behaviour of their potential prey is also affected, with the nymphs' growth rate being slowed by the need to hide rather than feed. Other nematodes turn adult male mayflies into quasi females which haunt the edges of streams, enabling the parasites to break their way out into the aqueous environment they need to complete their life cycles. The nymphs can also serve as intermediate hosts for the horsehair worm Paragordius varius, which causes its definitive host, a grasshopper, to jump into water and drown.

Mayflies are involved in both primary production and bioturbation. A study in laboratory simulated streams revealed that the mayfly genus Centroptilum increased the export of periphyton, thus indirectly affecting primary production positively, which is an essential process for ecosystems. The mayfly can also reallocate and alter the nutrient availability in aquatic habitats through the process of bioturbation. By burrowing in the bottom of lakes and redistributing nutrients, mayflies indirectly regulate phytoplankton and epibenthic primary production. Once burrowing to the bottom of the lake, mayfly nymphs begin to billow their respiratory gills. This motion creates current that carries food particles through the burrow and allows the nymph to filter feed. Other mayfly nymphs possess elaborate filter feeding mechanisms like that of the genus Isonychia. The nymph have forelegs that contain long bristle like structures that have two rows of hairs. Interlocking hairs form the filter by which the insect traps food particles. The action of filter feeding has a small impact on water purification but an even larger impact on the convergence of small particulate matter into matter of a more complex form that goes on to benefit consumers later in the food chain.

Mayflies are distributed all over the world in clean freshwater habitats, They tend to be absent from oceanic islands or represented by one or two species that have dispersed from nearby mainland. Female mayflies may be dispersed by wind, and eggs may be transferred by adhesion to the legs of waterbirds. The greatest generic diversity is found in the Neotropical realm, while the Holarctic has a smaller number of genera but a high degree of speciation. Some thirteen families are restricted to a single bioregion. The main families have some general habitat preferences: the Baetidae favour warm water; the Heptageniidae live under stones and prefer fast flowing water; and the relatively large Ephemeridae make burrows in sandy lake or river beds.

The nymph is the dominant life history stage of the mayfly. Different insect species vary in their tolerance to water pollution, but in general, the larval stages of mayflies, stoneflies (Plecoptera) and caddis flies (Trichoptera) are susceptible to a number of pollutants including sewage, pesticides and industrial effluent. In general, mayflies are particularly sensitive to acidification, but tolerances vary, and certain species are exceptionally tolerant to heavy metal contamination and to low pH levels. Ephemerellidae are among the most tolerant groups and Siphlonuridae and Caenidae the least. The adverse effects on the insects of pollution may be either lethal or sub lethal, in the latter case resulting in altered enzyme function, poor growth, changed behaviour or lack of reproductive success. As important parts of the food chain, pollution can cause knock on effects to other organisms; a dearth of herbivorous nymphs can cause overgrowth of algae, and a scarcity of predacious nymphs can result in an over abundance of their prey species. Fish that feed on mayfly nymphs that have bioaccumulated heavy metals are themselves at risk. Adult female mayflies find water by detecting the polarization of reflected light. They are easily fooled by other polished surfaces which can act as traps for swarming mayflies. The status of many species of mayflies is unknown because they are known from only the original collection data. Four North American species are believed to be extinct. Among these, Pentagenia robusta was originally collected from the Ohio River near Cincinnati, but this species has not been seen since its original collection in the 1800s. Ephemera compar is known from a single specimen, collected from the "foothills of Colorado" in 1873, but despite intensive surveys of the Colorado mayflies reported in 1984, it has not been rediscovered. The International Union for Conservation of Nature (IUCN) red list of threatened species includes one mayfly: Tasmanophlebia lacuscoerulei, the large blue lake mayfly, which is a native of Australia and is listed as endangered because its alpine habitat is vulnerable to climate change.

Mayflies are the primary source of models for artificial flies, hooks tied with coloured materials such as threads and feathers, used in fly fishing. In 1983, Patrick McCafferty recorded that artificial flies had been based on 36 genera of North American mayfly, from a total of 63 western species and 103 eastern/central species. A large number of these species have common names among fly fishermen, who need to develop a substantial knowledge of mayfly "habitat, distribution, seasonality, morphology and behavior" in order to match precisely the look and movements of the insects that the local trout are expecting. Nymph or "wet fly" fishing was restored to popularity on the chalk streams of England by G. E. M. Skues with his 1910 book Minor Tactics of the Chalk Stream. In the book, Skues discusses the use of duns to catch trout. The March brown is "probably the most famous of all British mayflies", having been copied by anglers to catch trout for over 500 years. Some English public houses beside trout streams such as the River Test in Hampshire are named "The Mayfly".

The hatch of the giant mayfly Palingenia longicauda on the Tisza and Maros Rivers in Hungary and Serbia, known as "Tisza blooming", is a tourist attraction. The 2014 hatch of the large black brown mayfly Hexagenia bilineata on the Mississippi River in the US was imaged on weather radar; the swarm flew up to 760 m (2,500 feet) above the ground near La Crosse, Wisconsin, creating a radar signature that resembled a "significant rain storm", and the mass of dead insects covering roads, cars and buildings caused a "slimy mess". During the weekend of 13–14 June 2015, a large swarm of mayflies caused several vehicular accidents on the Columbia–Wrightsville Bridge, carrying Pennsylvania Route 462 across the Susquehanna River between Columbia and Wrightsville, Pennsylvania. The bridge had to be closed to traffic twice during that period due to impaired visibility and obstructions posed by piles of dead insects.

Mayflies are consumed in several cultures and are estimated to contain the most raw protein content of any edible insect by dry weight. In Malawi, kungu, a paste of mayflies (Caenis kungu) and mosquitoes is made into a cake for eating. Adult mayflies are collected and eaten in many parts of China and Japan. Near Lake Victoria, Povilla mayflies are collected, dried and preserved for use in food preparations.

"Mayfly" was the crew's nickname for His Majesty's Airship No. 1, an aerial scout airship built by Vickers but wrecked by strong winds in 1911 before her trial flights. Two vessels of the Royal Navy were named : a torpedo boat launched in January 1907, and a Fly class river gunboat constructed in sections at Yarrow in 1915. The Seddon Mayfly, which was constructed in 1908, was an aircraft that was unsuccessful in early flight. The first aircraft designed by a woman, Lillian Bland, was titled the Bland Mayfly. Mayflies could find uses in the biomedical, pharmaceutical, and cosmetic industries. Their exoskeleton contains chitin, which has applications in these industries. Mayfly larvae do not survive in polluted aquatic habitats and, thus, have been chosen as bioindicators, markers of water quality in ecological assessments. In marketing, Nike produced a line of running shoes in 2003 titled "Mayfly". The shoes were designed with a wing venation pattern like the mayfly and were also said to have a finite lifetime. The telecommunication company Vodafone featured mayflies in a 2006 branding campaign, telling consumers to "make the most of now".