Editing Mayfly (section)

== Description ==

=== Nymph ===

{{multiple image|perrow=2/1|total_width=330|caption_align=center
| align = right
| image_style = border:none;
| image1 = Mayfly nymph dorsal view wing buds paired gills.JPG
| alt1 =
| image2 = Leptophlebia.marginata.subimago.jpg
| alt2 =
| image3 = Mayfly instar.jpg
| alt3 =
| image4 = Eendagsvlieg (257301115).jpeg
| alt4 =
| footer = {{font|size=100%|font=Sans-serif|text=Top left: Mayfly nymph, dorsal view, showing the paired gills and three projections on the abdomen; wing buds are visible on the thorax. Top right: Subimago of ''[[Leptophlebia marginata]]''. Middle: Nymph of the mayfly ''[[Cloeon dipterum]]'', showing seven pairs of [[gill]]s along the sides of the abdomen. Bottom: Lateral view of mayfly [[Insect wing|wing]] translucent [[Iridescence#Examples|iridescence]].}}
}}

Immature mayflies are [[aquatic insect|aquatic]] and are referred to as nymphs or naiads. In contrast to their short lives as adults, they may live for several years in the water. They have an elongated, cylindrical or somewhat flattened body that passes through a number of [[instar]]s (stages), moulting and increasing in size each time. When ready to emerge from the water, nymphs vary in length, depending on species, from {{convert|3|to|30|mm|2|abbr=on}}.<ref name=McCafferty1983/> The [[insect morphology#Head|head]] has a tough outer covering of [[sclerotin]], often with various hard ridges and projections; it points either forwards or downwards, with the mouth at the front. There are two large [[arthropod eye|compound eyes]], three [[ocelli]] (simple eyes) and a pair of [[antenna (biology)|antennae]] of variable lengths, set between or in front of the eyes. The mouthparts are designed for chewing and consist of a flap-like [[labrum (arthropod mouthpart)|labrum]], a pair of strong [[mandible (insect mouthpart)|mandibles]], a pair of [[maxilla (arthropod mouthpart)|maxillae]], a membranous [[Insect mouthparts#Hypopharynx|hypopharynx]] and a [[labium (insect)|labium]].<ref name=Dominguez/>

The [[Insect morphology#Thorax|thorax]] consists of three segments – the hindmost two, the [[mesothorax]] and [[metathorax]], being fused. Each segment bears a pair of legs which usually terminate in a single claw. The legs are robust and often clad in bristles, hairs or spines. Wing pads develop on the mesothorax, and in some species, hindwing pads develop on the metathorax.<ref name=Dominguez/>

The [[Insect morphology#Abdomen|abdomen]] consists of ten segments, some of which may be obscured by a large pair of [[operculum (animal)|operculate]] gills, a thoracic shield (expanded part of the [[prothorax]]) or the developing wing pads. In most [[taxa]] up to seven pairs of [[gill]]s arise from the top or sides of the abdomen, but in some species they are under the abdomen, and in a very few species the gills are instead located on the [[arthropod leg|coxae]] of the legs, or the bases of the maxillae. The abdomen terminates in slender thread-like projections, consisting of a pair of [[Cercus|cerci]], with or without a third central [[caudal filament]].<!--<ref>Imms, A. D., rev. Richards, O. W. & Davies, R. G. (1970) ''A General Textbook of Entomology'' 9th Ed. Methuen 886 pp.</ref>{{Page needed}}--><ref name=Dominguez>{{cite book |last=Domínguez |first=Eduardo |title=Ephemeroptera de América Del Sur |url=https://books.google.com/books?id=dwaJWle8OfkC&pg=PA17 |year=2006 |publisher=[[Pensoft Publishers]] |isbn=978-954-642-259-0 |pages=17–24 }}</ref>

===Subimago===
{{Anchor|Subimago}}<!-- [[Subimago]] redirects here -->

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,<ref>{{cite news|title=Subimago | work=Britannica.com}}</ref> often has partially cloudy wings fringed with minute hairs known as microtrichia; its eyes, legs and [[Insect reproductive system|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.<ref>{{Cite journal |last1=Edmunds |first1=George F. |author1-link=George F. Edmunds (entomologist) |last2=McCafferty |first2=W. P. |date=1988 |title=The Mayfly Subimago |journal=Annual Review of Entomology |volume=33 |issue=1 |pages=509–527 |doi=10.1146/annurev.en.33.010188.002453 |issn=0066-4170}}</ref> 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.<ref name=McCafferty1983>{{cite book |last=McCafferty |first=W. Patrick |title=Aquatic Entomology: The Fishermen's and Ecologists' Illustrated Guide to Insects and Their Relatives |chapter-url=https://books.google.com/books?id=wiTq7x-fI_0C&pg=PA94 |year=1983 |publisher=[[Jones & Bartlett Learning|Jones & Bartlett]] |isbn=978-0-86720-017-1 |pages=91–123 |chapter=Mayflies}}</ref>

=== Imago ===

[[File:Mayfly - atalophlebia.jpg|thumb|upright|Adult ''[[Atalophlebia]]'' with the cylindrical dorsal or turban eyes visible]]

Adult mayflies, or [[imago]]s, 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.<ref>{{cite journal |last1=Thomas |first1=Jessica A. |last2=Trueman |first2=John W. H. |last3=Rambaut |first3=Andrew |last4=Welch |first4=John J. |year=2013 |title=Relaxed phylogenetics and the Palaeoptera problem: resolving deep ancestral splits in the insect phylogeny |journal=Systematic Biology |volume=62 |issue=2 |pages=285–297 |pmid=23220768 |doi=10.1093/sysbio/sys093 |doi-access=free }}</ref> Mayflies are delicate-looking insects with one or two pairs of membranous, triangular wings, which are extensively covered with [[Insect wing#Venation|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 (insect anatomy)|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.<ref>{{cite journal |last=Burghause |first=Frank |title=The structure of the double eyes of Baetis and the uniform eyes of Ecdyonurus (Ephemeroptera) |journal=Zoomorphology |year=1981 |volume=98 | pages=17–34 |doi=10.1007/BF00310318 |s2cid=36002849 }}</ref> They are capable of detecting ultraviolet light and are thought to be used during courtship to detect females flying above them.<ref name=polarized>{{cite book |last1=Horváth |first1=Gábor |last2=Varju |first2=Dezsö |title=Polarized Light in Animal Vision: Polarization Patterns in Nature |publisher=[[Springer Nature|Springer]] |year=2004 |pages=238–239}}</ref> 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 [[Cercus|cerci]] (tail-like appendages) at the tip. Like [[Entognatha]], [[Archaeognatha]] and [[Zygentoma]], the [[Spiracle (arthropods)|spiracles]] on the abdomen do not have closing muscles.<ref>[https://palivec.entu.cas.cz/~cizek/prednasky%20-%20JU/SystEnt12/Beutel2014-Insect-morphology.pdf Insect Morphology and Phylogeny (page 101)]</ref><ref>[https://www.zobodat.at/pdf/Ent-Abhandlungen-Dresden_61_0119-0172.pdf Proceedings of the 1st Dresden Meeting on Insect Phylogeny: "Phylogenetic Relationships within the Insect Orders". (Dresden, September 19-21, 2003) (page 7)]</ref> Uniquely among insects, mayflies possess paired genitalia, with the male having two [[aedeagi]] (penis-like organs) and the female two [[gonopore]]s (sexual openings).<ref name=IIBD/><ref name=McCafferty1983/>