Editing Mayfly (section)

=== 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/>