Editing Dragonfly (section)

==General description==
[[File:Damselfly October 2007 Osaka Japan.jpg|thumb|left|[[Damselflies]], like this ''[[Ischnura senegalensis]]'', are slenderer in build than dragonflies, and most hold their wings closed over their bodies.]]
[[File:Red dragonfly - Caldas de Monchique - The Algarve, Portugal (1388550112).jpg|thumb|left|Red dragonfly, [[Caldas de Monchique]], Portugal]]
Dragonflies (suborder Anisoptera) are heavy-bodied, strong-flying insects that hold their wings horizontally both in flight and at rest. By contrast, damselflies (suborder Zygoptera) have slender bodies and fly more weakly; most species fold their wings over the abdomen when stationary, and the eyes are well separated on the sides of the head.<ref name=diversity /><ref name=Ruppert>{{cite book |title=Invertebrate Zoology, 7th edition |last1=Ruppert |first1=Edward E. |last2=Fox |first2=Richard, S. |last3=Barnes |first3=Robert D. |year=2004 |publisher=Cengage Learning |isbn=978-81-315-0104-7 |page=745 }}</ref>

An adult dragonfly has three distinct segments, the head, thorax, and abdomen, as in all insects. It has a [[chitin]]ous exoskeleton of hard plates held together with flexible membranes. The head is large with very short [[Antenna (biology)|antennae]]. It is dominated by the two compound eyes, which cover most of its surface. The compound eyes are made up of [[ommatidia]], the numbers being greater in the larger species. ''Aeshna interrupta'' has 22650 ommatidia of two varying sizes, 4500 being large. The facets facing downward tend to be smaller. ''[[Petalura gigantea]]'' has 23890 ommatidia of just one size. These facets provide complete vision in the frontal hemisphere of the dragonfly.<ref>{{cite journal|title=On the morphology of the compound eyes of dragonflies (Odonata: Anisoptera), with special reference to their role in prey capture|last=Pritchard|first=Gordon|doi=10.1111/j.1365-3032.1966.tb01126.x| year=1966| journal=Proceedings of the Royal Entomological Society of London|volume= 41|issue=1–3|pages=1–8 }}</ref> The compound eyes meet at the top of the head (except in the Petaluridae and Gomphidae, as also in the genus ''[[Epiophlebia]]''). Also, they have three [[Simple eye in invertebrates|simple eyes]] or ocelli. The mouthparts are adapted for biting with a toothed jaw; the flap-like [[Labrum (arthropod mouthpart)|labrum]], at the front of the mouth, can be shot rapidly forward to catch [[Predation|prey]].<ref name="UCMP-Berkeley"/>{{sfn|Berger|2004|pp=5–6}} The head has a system for locking it in place that consists of muscles and small hairs on the back of the head that grip structures on the front of the first thoracic segment. This arrester system is unique to the Odonata, and is activated when feeding and during tandem flight.<ref name=diversity />

[[File:Dragonfly anatomy.svg|thumb|upright=2|Anatomy of a dragonfly]]

The thorax consists of three segments as in all insects. The [[prothorax]] is small and flattened dorsally into a shield-like disc, which has two transverse ridges. The [[mesothorax]] and [[metathorax]] are fused into a rigid, box-like structure with internal bracing, and provide a robust attachment for the powerful wing muscles inside.<ref name=Needham>{{cite book|last=Needham |first=J.G.|title=A Manual of the Dragonflies of North America|url=https://books.google.com/books?id=WSV1lpI262wC&pg=PA10 |year=1975 |publisher=[[University of California Press]] |pages=10–21|id=GGKEY:5YCUC2C45TH}}</ref> The thorax bears two pairs of wings and three pairs of legs. The wings are long, veined, and membranous, narrower at the tip and wider at the base. The hindwings are broader than the forewings and the venation is different at the base.<ref name="Paulson2011"/> The veins carry [[haemolymph]], which is analogous to blood in vertebrates, and carries out many similar functions, but which also serves a hydraulic function to expand the body between nymphal stages ([[instar]]s) and to expand and stiffen the wings after the adult emerges from the final nymphal stage. The leading edge of each wing has a node where other veins join the marginal vein, and the wing is able to flex at this point. In most large species of dragonflies, the wings of females are shorter and broader than those of males.{{sfn|Berger|2004|pp=5–6}} The legs are rarely used for walking, but are used to catch and hold prey, for perching, and for climbing on plants. Each has two short basal joints, two long joints, and a three-jointed foot, armed with a pair of claws. The long leg joints bear rows of spines, and in males, one row of spines on each front leg is modified to form an "eyebrush", for cleaning the surface of the compound eye.<ref name=Needham/>

[[File:A migrant hawker dragonfly.jpg|thumb|upright=0.7|left|Migrant hawker, ''[[Aeshna mixta]]'', has the long, slender abdomen of [[Aeshnidae|aeshnid]] dragonflies.]]

The abdomen is long and slender and consists of 10 segments. Three [[Cercus|terminal appendages]] are on segment 10; a pair of superiors (claspers) and an inferior. The second and third segments are enlarged, and in males, the underside of the second segment has a cleft, forming the secondary genitalia consisting of the [[Lamina (anatomy)|lamina]], hamule, genital lobe, and penis. There are remarkable variations in the presence and the form of the penis and the related structures, the [[flagellum]], cornua, and genital lobes. Sperm is produced at the ninth segment, and is transferred to the secondary genitalia prior to mating. The male holds the female behind the head using a pair of claspers on the terminal segment. In females, the genital opening is on the underside of the eighth segment, and is covered by a simple flap (vulvar lamina) or an [[ovipositor]], depending on species and the method of egg-laying. Dragonflies having simple flaps shed the eggs in water, mostly in flight. Dragonflies having ovipositors use them to puncture soft tissues of plants and place the eggs singly in each puncture they make.<ref name=Needham/><ref name="Miller">{{cite journal |last1=Miller |first1=P. L. |title=The structure and function of the genitalia in the Libellulidae (Odonata) |journal=Zoological Journal of the Linnean Society |date=1991 |volume=102 |issue=1 |pages=43–73 |doi=10.1111/j.1096-3642.1991.tb01536.x }}</ref><ref name="Miller2">{{cite journal |last1=Miller |first1=P. L. |title=Sperm competition and penis structure in some Libellulid dragonflies (Anisoptera) |journal=Odonatologica |date=1995 |volume=24 |issue=1 |pages=63–72 |url=http://natuurtijdschriften.nl/download?type=document;docid=592110 |access-date=21 November 2018}}</ref><ref name="Battin">{{cite journal |last1=Battin |first1=Tom J. |title=The odonate mating system, communication, and sexual selection: A review |journal=Italian Journal of Zoology |date=1993 |volume=60 |issue=4 |pages=353–360 |doi=10.1080/11250009309355839 |doi-access=free }}</ref>

Dragonfly nymphs vary in form with species, and are loosely classed into claspers, sprawlers, hiders, and burrowers.<ref name=diversity /> The first instar is known as a prolarva, a relatively inactive stage from which it quickly moults into the more active nymphal form.<ref name=resh>{{cite book|pages=[https://archive.org/details/encyclopediainse00resh_059/page/n757 721]–729|chapter=Odonata (Dragonflies, Damselflies)|last=Tennessen, K.J.|title=Encyclopedia of Insects|url=https://archive.org/details/encyclopediainse00resh_059|url-access=limited|editor1-last=Resh |editor1-first=Vincent H. |editor2-last=Carde |editor2-first=Ring T. |year=2009|edition=2|publisher=Academic Press}}</ref> The general body plan is similar to that of an adult, but the nymph lacks wings and reproductive organs. The lower jaw has a huge, extensible [[Insect mouthparts#Labium|labium]], armed with hooks and spines, which is used for catching prey. This labium is folded under the body at rest and struck out at great speed by hydraulic pressure created by the abdominal muscles.<ref name=diversity /> Both damselfly and dragonfly nymphs ventilate the rectum, but just some damselfly nymphs have a rectal epithelium that is rich in [[Trachea#Invertebrates|trachea]], relying mostly on three feathery external [[gill]]s as their major source of respiration. Only dragonfly nymphs have internal gills, called a branchial chamber, located around the fourth and fifth abdominal segments. These internal gills consist originally of six longitudinal folds, each side supported by cross-folds. But this system has been modified in several families. Water is pumped in and out of the abdomen through an opening at the tip. The naiads of some clubtails ([[Gomphidae]]) that burrow into the sediment, have a snorkel-like tube at the end of the abdomen enabling them to draw in clean water while they are buried in mud. Naiads can forcefully expel a jet of water to propel themselves with great rapidity.<ref name=Lawlor/><ref>[https://books.google.com/books?id=efddAAAAQBAJ&dq=both+odonate+suborders+ventilate+the+rectum&pg=PT103 Aquatic Entomology]</ref><ref>[https://books.google.com/books?id=VgyM-fCmrHEC&dq=%22+Anisopteran+larvae+are+unique+in+that+their+tracheal+gills+lie+in+the+modified+anterior+region+of+the+rectum%22&pg=PA11 Insect Physiology]</ref>

=== Color<!-- yes, this IS the British English spelling  Really? The American habit of dropping "u" from aluminium, neighbour, humour etc is well-documented. I'm 99.9% sure colour is considered correct in britenglish -->ation ===
[[File:Big Eyes (8753086631).jpg|thumb|left|[[Iridescent]] [[structural coloration]] in a dragonfly's eyes]]

Many adult dragonflies have brilliant [[iridescent]] or metallic colours produced by [[structural colouration]]<!--both UK and US-->, making them conspicuous in flight. Their overall [[animal coloration|color<!-- yes, this IS the British English spelling -->ation]] is often a combination of yellow, red, brown, and black pigments, with structural colours. Blues are typically created by microstructures in the cuticle that reflect blue light. Greens often combine a structural blue with a yellow pigment. Freshly emerged adults, known as tenerals, are often pale, and obtain their typical colours after a few days.<ref name="Paulson2011">{{cite book |last=Paulson |first=Dennis |title=Dragonflies and Damselflies of the East |url=https://books.google.com/books?id=dTpjGOiHwNkC&pg=PA29 |year=2011 |publisher=[[Princeton University Press]] |isbn=978-1-4008-3966-7 |pages=29–32}}</ref> Some have their bodies covered with a pale blue, waxy powderiness called pruinosity; it wears off when scraped during mating, leaving darker areas.{{sfn|Powell|1999|page=102}}

[[File:Img 041538 mating anax junius.jpg|thumb|Male green darner, ''[[Anax junius]]'' has noniridescent structural blue; the female (below) lacks the colour.]]

Some dragonflies, such as the green darner, ''[[Anax junius]]'', have a noniridescent blue that is produced structurally by scatter from arrays of tiny spheres in the [[endoplasmic reticulum]] of epidermal cells underneath the cuticle.<ref>{{cite journal |last1=Prum |first1=Richard O. |author-link=Richard O. Prum |last2=Cole |first2=Jeff A.|last3=Torres |first3=Rodolfo H. |author3-link= Rodolfo H. Torres |title=Blue integumentary structural colours in dragonflies (Odonata) are not produced by incoherent Tyndall scattering |journal=Journal of Experimental Biology |date=15 October 2004 |volume=207 |issue=22 |pages=3999–4009 |doi=10.1242/jeb.01240 |pmid=15472030|hdl=1808/1601 |s2cid=15900357 |url=https://kuscholarworks.ku.edu/bitstream/1808/1601/1/3999.pdf|doi-access=free |bibcode=2004JExpB.207.3999P }}</ref>

The wings of dragonflies are generally clear, apart from the dark veins and pterostigmata. In the chasers (Libellulidae), however, many genera have areas of colour on the wings: for example, groundlings (''[[Brachythemis]]'') have brown bands on all four wings, while some scarlets (''[[Crocothemis]]'') and dropwings (''[[Trithemis]]'') have bright orange patches at the wing bases. Some aeshnids such as the brown hawker (''[[Aeshna grandis]]'') have translucent, pale yellow wings.{{sfn|Dijkstra|2006|pages=26–35}}

Dragonfly nymphs are usually a well-[[camouflage]]d blend of dull brown, green, and grey.<ref name=Lawlor/>