Editing Dragonfly (section)

==Biology==

===Ecology===

Dragonflies and damselflies are predatory both in the aquatic nymphal and adult stages. Nymphs feed on a range of freshwater invertebrates and larger ones can prey on [[tadpole]]s and small [[fish]].{{sfn|Dijkstra|2006|pages=8–9}} Naiads of one species, ''[[Phanogomphus militaris]]'', may even act as parasites, feeding on the gills of gravid freshwater mussels.<ref>{{cite journal |last1=Levine |first1=Todd D. |last2=Lang |first2=Brian K. |last3=Berg |first3=David J. |title=Parasitism of Mussel Gills by Dragonfly Nymphs |journal=The American Midland Naturalist |year=2009 |volume=162 |issue=1 |pages=1–6 |doi=10.1674/0003-0031-162.1.1}}</ref> Adults capture insect prey in the air, making use of their acute vision and highly controlled flight.

[[File:Dragonfly catches flying prey.webm|thumb|center|thumbtime=0|Dragonfly returns to same perch each time it darts out to catch very small flying prey.]]

The mating system of dragonflies is complex, and they are among the few insect groups that have a system of indirect sperm transfer along with sperm storage, delayed fertilisation, and sperm competition.{{sfn|Dijkstra|2006|pages=8–9}}

Adult males vigorously defend territories near water; these areas provide suitable habitat for the nymphs to develop, and for females to lay their eggs. Swarms of feeding adults aggregate to prey on swarming prey such as emerging flying ants or termites.{{sfn|Dijkstra|2006|pages=8–9}}

[[File:Libellula quadrimaculata m1.jpg|thumb|Habitat preference: A four-spotted chaser, ''[[Libellula quadrimaculata]]'' on an [[emergent vegetation|emergent plant]], the water violet ''[[Hottonia palustris]]'', with submerged vegetation in the background]]

Dragonflies as a group occupy a considerable variety of habitats, but many species, and some families, have their own specific environmental requirements.{{sfn|Dijkstra|2006|pages=13–14}} Some species prefer flowing waters, while others prefer standing water. For example, the Gomphidae (clubtails) live in running water, and the Libellulidae (skimmers) live in still water.{{sfn|Dijkstra|2006|pages=13–14}} Some species live in temporary water pools and are capable of tolerating changes in water level, desiccation, and the resulting variations in temperature, but some genera such as ''[[Sympetrum]]'' (darters)  have eggs and nymphs that can resist drought and are stimulated to grow rapidly in warm, shallow pools, also often benefiting from the absence of predators there.{{sfn|Dijkstra|2006|pages=13–14}} Vegetation and its characteristics including submerged, floating, emergent, or waterside are also important. Adults may require emergent or waterside plants to use as perches; others may need specific submerged or floating plants on which to lay eggs. Requirements may be highly specific, as in ''[[Aeshna viridis]]'' (green hawker), which lives in swamps with the water-soldier, ''[[Stratiotes aloides]]''.{{sfn|Dijkstra|2006|pages=13–14}} The chemistry of the water, including its trophic status (degree of enrichment with nutrients) and [[pH]] can also affect its use by dragonflies. Most species need moderate conditions, not too [[eutrophic]], not too acidic;{{sfn|Dijkstra|2006|pages=13–14}} a few species such as ''[[Sympetrum danae]]'' (black darter) and ''[[Libellula quadrimaculata]]'' (four-spotted chaser) prefer acidic waters such as peat bogs,{{sfn|Dijkstra|2006|pages=243, 272}} while others such as ''[[Libellula fulva]]'' (scarce chaser) need slow-moving, eutrophic waters with reeds or similar waterside plants.{{sfn|Dijkstra|2006|page=246}}<ref name="Ratcliffe2012">{{cite book |last=Ratcliffe |first=Derek |title=A Nature Conservation Review: Volume 1: The Selection of Biological Sites of National Importance to Nature Conservation in Britain |url=https://books.google.com/books?id=YPQaFxH-AZYC&pg=PA378 |date=26 January 2012 |publisher=[[Cambridge University Press]] |isbn=978-0-521-20329-6 |pages=378–379}}</ref>

===Behaviour===
[[File:Small pincertail (Onychogomphus forcipatus) male Bulgaria.jpg|thumb|''[[Onychogomphus forcipatus]]'' male in Bulgaria]]
Many dragonflies, particularly males, are [[Territory (animal)|territorial]]. Some defend a territory against others of their own species, some against other species of dragonfly and a few against insects in unrelated groups. A particular perch may give a dragonfly a good view over an insect-rich feeding ground; males of many species such as the [[blue dasher|''Pachydiplax longipennis'']] (blue dasher) jostle other dragonflies to maintain the right to alight there.{{sfn|Berger|2004|pp=32–34}} Defending a breeding territory is common among male dragonflies, especially in species that congregate around ponds. The territory contains desirable features such as a sunlit stretch of shallow water, a special plant species, or the preferred [[Substrate (biology)|substrate]] for egg-laying. The territory may be small or large, depending on its quality, the time of day, and the number of competitors, and may be held for a few minutes or several hours. Dragonflies including [[black saddlebags|''Tramea lacerata'']] (black saddlebags) may notice landmarks that assist in defining the boundaries of the territory. Landmarks may reduce the costs of territory establishment, or might serve as a spatial reference.<ref>{{Cite journal |last1=Lojewski |first1=Jeffrey A. |last2=Switzer |first2=Paul V. |title=The role of landmarks in territory maintenance by the black saddlebags dragonfly, Tramea lacerata |url=https://doi.org/10.1007/s00265-014-1847-z |journal=Behavioral Ecology and Sociobiology |date=1 March 2015 |volume=69 |issue=3 |pages=347–355 |doi=10.1007/s00265-014-1847-z |bibcode=2015BEcoS..69..347L |s2cid=17617885 |issn=1432-0762}}</ref> Some dragonflies signal ownership with striking colours on the face, abdomen, legs, or wings. The [[common whitetail|''Plathemis lydia'']] (common whitetail) dashes towards an intruder holding its white abdomen aloft like a flag. Other dragonflies engage in aerial dogfights or high-speed chases. A female must mate with the territory holder before laying her eggs.{{sfn|Berger|2004|pp=32–34}} There is also [[Sexual conflict|conflict]] between the males and females. Females may sometimes be harassed by males to the extent that it affects their normal activities including foraging and in some dimorphic species females have evolved multiple forms with some forms appearing deceptively like males.<ref>{{cite journal |last=Fincke |first=Ola M. |title=Polymorphic signals of harassed female odonates and the males that learn them support a novel frequency-dependent model |journal=Animal Behaviour |year=2004 |volume=67 |issue=5 |pages=833–845 |doi=10.1016/j.anbehav.2003.04.017 |s2cid=15705194 }}</ref> In some species females have evolved behavioural responses such as feigning death to escape the attention of males.<ref>{{cite journal |last=Khelifa |first=Rassim |title=Faking death to avoid male coercion: Extreme sexual conflict resolution in a dragonfly |journal=Ecology |year=2017 |volume=98 |issue=6 |pages=1724–1726 |doi=10.1002/ecy.1781 |pmid=28436995|bibcode=2017Ecol...98.1724K |s2cid=42601970 }}</ref> Similarly, selection of habitat by adult dragonflies is not random, and terrestrial habitat patches may be held for up to 3 months. A species tightly linked to its birth site utilises a foraging area that is several orders of magnitude larger than the birth site.<ref>{{Cite journal |last1=Dolný|first1=Aleš |last2=Harabiš |first2=Filip |last3=Mižičová |first3=Hana |date=2014-07-09 |title=Home Range, Movement, and Distribution Patterns of the Threatened Dragonfly Sympetrum depressiusculum (Odonata: Libellulidae): A Thousand Times Greater Territory to Protect? |journal=PLOS ONE |volume=9 |issue=7 |pages=e100408 |doi=10.1371/journal.pone.0100408 |pmid=25006671 |pmc=4090123 |bibcode=2014PLoSO...9j0408D |issn=1932-6203|doi-access=free }}</ref>

=== Reproduction ===

[[File:Orthetrum luzonicum mating of Kadavoor.jpg|thumb|upright|Mating pair of marsh skimmers, ''[[Orthetrum luzonicum]]'', forming a "heart"]]
[[File:Dragonflies on pond.webm|thumb|thumbtime=148|right|Dragonflies over a pond (including female inserting eggs below the water surface.]]

Mating in dragonflies is a complex, precisely choreographed process. First, the male has to attract a female to his territory, continually driving off rival males. When he is ready to mate, he transfers a packet of sperm from his primary genital opening on segment 9, near the end of his abdomen, to his secondary genitalia on segments 2–3, near the base of his abdomen. The male then grasps the female by the head with the claspers at the end of his abdomen; the structure of the claspers varies between species, and may help to prevent interspecific mating.<ref name=Cordero>{{cite book |last1=Cordero-Rivera |first1=Adolfo |last2=Cordoba-Aguilar |first2=Alex |title=15. Selective Forces Propelling Genitalic Evolution in Odonata |year=2010 |page=343 |url=http://ecoevo.uvigo.es/pdf/2010/2010-Genital%20evolution%20odonata-lq.pdf}}</ref> The pair flies in tandem with the male in front, typically perching on a twig or plant stem. The female then curls her abdomen downwards and forwards under her body to pick up the sperm from the male's secondary genitalia, while the male uses his "tail" claspers to grip the female behind the head: this distinctive posture is called the "heart" or "wheel";{{sfn|Dijkstra|2006|pages=8–9}}{{sfn|Trueman|Rowe|2009|page=Life Cycle and Behavior}} the pair may also be described as being "in cop".<ref>{{harvnb|Berger|2004|p=39}}: "Romantic souls are pleased to note that at the climactic moment, the two slender bodies form a delicate heart shape. Experts say the pair is now 'in cop'."</ref>

Egg-laying (ovipositing) involves not only the female darting over floating or waterside vegetation to deposit eggs on a suitable substrate, but also the male hovering above her or continuing to clasp her and flying in tandem. This behaviour following the transfer of sperm is termed as mate guarding and the guarding male attempts to increase the probability of his sperm fertilising eggs. [[Sexual selection]] with sperm competition occurs within the spermatheca of the female and sperm can remain viable for at least 12 days in some species.<ref>{{Cite journal |last=Reinhardt |first=Klaus |date=2005 |title=Sperm numbers, sperm storage duration and fertility limitation in the Odonata |url=https://worlddragonfly.org/article/13887890-2005-9748242/ |journal=International Journal of Odonatology |volume=8 |issue=1 |pages=45–58 |doi=10.1080/13887890.2005.9748242 |issn=1388-7890 |doi-access=free |bibcode=2005IJOdo...8...45R }}</ref><ref name=Carde>{{cite book |author1=Cardé, Ring T. |author2= Resh, Vincent H. |title=A World of Insects: The Harvard University Press Reader |url=https://books.google.com/books?id=g28jXs3CVC8C&pg=PA195 |year=2012 |publisher=[[Harvard University Press]] |isbn=978-0-674-04619-1 |pages=195–197}}</ref> Females can fertilise their eggs using sperm from the spermatheca at any time.{{sfn|Dijkstra|2006|pages=8–9}}{{sfn|Trueman|Rowe|2009|page=Life Cycle and Behavior}}<ref name=Cordero/>  Males use their penis and associated genital structures to compress or scrape out sperm from previous matings; this activity takes up much of the time that a copulating pair remains in the heart posture.{{sfn|Berger|2004|p=39}} Flying in tandem has the advantage that less effort is needed by the female for flight and more can be expended on egg-laying, and when the female submerges to deposit eggs, the male may help to pull her out of the water.<ref name=Carde/>

Egg-laying takes two different forms depending on the species. The female in some families (Aeshnidae, Petaluridae) has a sharp-edged ovipositor with which she slits open a stem or leaf of a plant on or near the water, so she can push her eggs inside. In other families such as clubtails (Gomphidae), cruisers (Macromiidae), emeralds (Corduliidae), and skimmers (Libellulidae), the female lays eggs by tapping the surface of the water repeatedly with her abdomen, by shaking the eggs out of her abdomen as she flies along, or by placing the eggs on vegetation.{{sfn|Berger|2004|p=39}} In a few species, the eggs are laid on emergent plants above the water, and development is delayed until these have withered and become immersed.<ref name=Lawlor>{{cite book |last=Lawlor |first=Elizabeth P. |title=Discover Nature in Water & Wetlands: Things to Know and Things to Do |url=https://books.google.com/books?id=Xo83huW7O6YC&pg=PA94 |year=1999 |publisher=Stackpole Books |isbn=978-0-8117-2731-0 |pages=88, 94–96}}</ref>

=== Life cycle ===

[[File:Larve d'Anax empereur.JPG|thumb|left|Nymph of emperor dragonfly, ''[[Anax imperator]]'']]
[[File:Dragonfly naiad mask.jpg|thumb|Illustration of a naiad with mask extended]]

Dragonflies are [[Hemimetabolism|hemimetabolous]] insects; they do not have a [[pupa]]l stage and undergo an incomplete [[metamorphosis]] with a series of nymphal stages from which the adult emerges.<ref name=IFAS>{{cite web |url=http://entomology.ifas.ufl.edu/creatures/misc/odonata/odonata.htm |title=Dragonflies and damselflies: Odonata |author=Bybee, Seth |date=1 May 2012 |work=Featured Creatures |publisher=University of Florida: Entomology and Nematology |access-date=1 March 2015}}</ref> Eggs laid inside plant tissues are usually shaped like grains of rice, while other eggs are the size of a pinhead, ellipsoidal, or nearly spherical. A clutch may have as many as 1500 eggs, and they take about a week to hatch into aquatic [[Nymph (biology)|nymphs]] or naiads which moult between six and 15 times (depending on species) as they grow.<ref name=diversity /> Most of a dragonfly's life is spent as a nymph, beneath the water's surface. The nymph extends its hinged labium (a toothed mouthpart similar to a lower mandible, which is sometimes termed as a "mask" as it is normally folded and held before the face) that can extend forward and retract rapidly to capture prey such as [[mosquito]] larvae, [[tadpole]]s, and small fish.<ref name=IFAS/> They breathe through gills in their [[rectum]], and can rapidly propel themselves by suddenly expelling water through the anus.<ref>{{cite journal |last1=Mill |first1=P. J. |last2=Pickard |first2=R. S. |year=1975 |title=Jet-propulsion in anisopteran dragonfly nymphs |journal=Journal of Comparative Physiology A |volume=97 |issue=4 |pages=329–338 |doi=10.1007/BF00631969|s2cid=45066664 }}</ref> Some naiads, such as the later stages of ''[[Antipodophlebia asthenes]]'', hunt on land.<ref>{{cite journal |title=Biology of odonata |journal=Annual Review of Entomology |year=1980 |volume=25 |pages=189–217 |last=Corbet |first=Philip S. |doi=10.1146/annurev.en.25.010180.001201}}</ref>

[[File:Anax Imperator 2(loz).JPG|thumb|upright|[[Ecdysis]]: [[Emperor (dragonfly)|Emperor dragonfly]], ''[[Anax imperator]]'', newly emerged and still soft, holding on to its dry [[exuvia]], and expanding its wings]]

The nymph stage of dragonflies lasts up to five years in large species, and between two months and three years in smaller species. When the naiad is ready to metamorphose into an adult, it stops feeding and makes its way to the surface, generally at night. It remains stationary with its head out of the water, while its respiration system adapts to breathing air, then climbs up a [[Phragmites|reed]] or other emergent plant, and moults ([[ecdysis]]). Anchoring itself firmly in a vertical position with its claws, its [[exoskeleton]] begins to split at a weak spot behind the head. The adult dragonfly crawls out of its nymph [[exoskeleton]], the [[exuvia]], arching backwards when all but the tip of its abdomen is free, to allow its exoskeleton to harden. Curling back upwards, it completes its emergence, swallowing air, which plumps out its body, and pumping [[haemolymph]] into its wings, which causes them to expand to their full extent.{{sfn|Berger|2004|pp=10–11}}

Dragonflies in temperate areas can be categorized into two groups: an early group and a later one. In any one area, individuals of a particular "spring species" emerge within a few days of each other. The [[Basiaeschna|springtime darner]] (''Basiaeschna janata''), for example, is suddenly very common in the spring, but disappears a few weeks later and is not seen again until the following year. By contrast, a "summer species" emerges over a period of weeks or months, later in the year. They may be seen on the wing for several months, but this may represent a whole series of individuals, with new adults hatching out as earlier ones complete their lifespans.{{sfn|Berger|2004|p=9}}

=== Sex ratios ===

The [[sex ratio]] of male to female dragonflies varies both temporally and spatially. Adult dragonflies have a high male-biased ratio at breeding habitats. The male-bias ratio has contributed partially to the females using different habitats to avoid male harassment. As seen in Hine's emerald dragonfly (''[[Somatochlora hineana]]''), male populations use wetland habitats, while females use dry meadows and marginal breeding habitats, only migrating to the wetlands to lay their eggs or to find mating partners. Unwanted mating is energetically costly for females because it affects the amount of time that they are able to spend foraging.<ref>{{cite journal |last1=Foster |first1=S.E |last2=Soluk |first2=D.A  |title=Protecting more than the wetland: The importance of biased sex ratios and habitat segregation for conservation of the Hine's emerald dragonfly, ''Somatochlora hineana'' Williamson |journal=Biological Conservation |year=2006 |pages=158–166 |doi=10.1016/j.biocon.2005.08.006 |volume=127|issue=2 |bibcode=2006BCons.127..158F }}</ref>

[[File:Brown Hawker Dragonfly in flight 7 (3877783853).jpg|thumb|Brown hawker, ''[[Aeshna grandis]]'' in flight: The hindwings are about 90° [[out of phase]] with the forewings at this instant, suggesting fast flight.]]

=== Flight ===

[[File:Voo nupcial detail.jpg|thumb|upright|Red-veined darters (''[[Sympetrum fonscolombii]]'') in [[mate guarding]] position with male above clasping the female behind the neck]]

Dragonflies are powerful and agile fliers, capable of [[insect migration|migrating]] across the sea, moving in any direction, and changing direction suddenly. In flight, the adult dragonfly can propel itself in six directions: upward, downward, forward, backward, to left and to right.<ref>{{cite book |last=Waldbauer |first=Gilbert |title=A Walk Around the Pond: Insects in and Over the Water |publisher=[[Harvard University Press]] |year=2006 |page=[https://archive.org/details/walkaroundpondin0000wald/page/105 105] |isbn=9780674022119 |url=https://archive.org/details/walkaroundpondin0000wald|url-access=registration }}</ref> They have four different styles of flight.<ref name="TOL-flight">{{cite web |last1=Rowe |first1=Richard J. |title=Dragonfly Flight |url=http://tolweb.org/notes/?note_id=2471 |website=Tree of Life |access-date=26 February 2015}}</ref>

* Counter-stroking, with forewings beating 180° [[out of phase]] with the hindwings, is used for hovering and slow flight. This style is efficient and generates a large amount of lift.
* Phased-stroking, with the hindwings beating 90° ahead of the forewings, is used for fast flight. This style creates more thrust, but less lift than counter-stroking.
* Synchronised-stroking, with forewings and hindwings beating together, is used when changing direction rapidly, as it maximises thrust.
* Gliding, with the wings held out, is used in three situations: free gliding, for a few seconds in between bursts of powered flight; gliding in the updraft at the crest of a hill, effectively hovering by falling at the same speed as the updraft; and in certain dragonflies such as darters, when "in cop" with a male, the female sometimes simply glides while the male pulls the pair along by beating his wings.<ref name="TOL-flight"/>

[[File:Dragonfly in flight 5 (1351481586).jpg|thumb|left|Southern hawker, ''[[Aeshna cyanea]]'': its wings at this instant are synchronised for agile flight.]]
The wings are [[Insect flight#Direct flight|powered directly]], unlike most families of insects, with the flight muscles attached to the wing bases. Dragonflies have a high power/weight ratio, and have been documented accelerating at 4 G linearly and 9 G in sharp turns while pursuing prey.<ref name="TOL-flight"/>

Dragonflies generate lift in at least four ways at different times, including classical [[lift (force)|lift]] like an aircraft [[wing]]; supercritical lift with the wing above the critical angle, generating high lift and using very short strokes to avoid stalling; and [[vortex shedding|creating and shedding vortices]]. Some families appear to use special mechanisms, as for example the Libellulidae which take off rapidly, their wings beginning pointed far forward and twisted almost vertically. Dragonfly wings behave highly dynamically during flight, flexing and twisting during each beat. Among the variables are wing curvature, length and speed of stroke, [[angle of attack]], forward/back position of wing, and phase relative to the other wings.<ref name="TOL-flight"/>

==== Flight speed ====

Old and unreliable claims are made that dragonflies such as the [[Austrophlebia costalis|southern giant darner]] can fly up to {{convert|97|kph|mph|abbr=on}}.<ref>{{cite book |last=Tillyard |first=Robert John |title=The Biology of Dragonflies |year=1917 |pages=322–323 |url=http://medusa.jcu.edu.au/odonata_digital_literature/Tillyard/tillyard_1917_book_searchable.pdf |access-date=15 December 2010 |quote=I doubt if any greater speed than this occurs amongst Odonata |archive-date=3 July 2017 |archive-url=https://web.archive.org/web/20170703054703/http://medusa.jcu.edu.au/odonata_digital_literature/Tillyard/tillyard_1917_book_searchable.pdf |url-status=dead }}</ref> However, the greatest reliable flight speed records are for other types of insects.<ref>{{cite web |title=Chapter 1 — Fastest Flyer |url=http://www.entnemdept.ufl.edu/walker/ufbir/chapters/chapter_01.shtml |author=Dean, T. J. |publisher=[[University of Florida]] |date=2003-05-01 |work=Book of Insect Records |url-status=dead |archive-url=https://web.archive.org/web/20110720083508/http://www.entnemdept.ufl.edu/walker/ufbir/chapters/chapter_01.shtml |archive-date=20 July 2011}}</ref> In general, large dragonflies like the hawkers have a maximum speed of {{convert|36|–|54|kph|mph|abbr=on}} with average cruising speed of about {{convert|16|kph|mph|abbr=on}}.<ref name="FAQ">{{cite web |title=Frequently Asked Questions about Dragonflies |url=http://www.british-dragonflies.org.uk/content/frequently-asked-questions |publisher=[[British Dragonfly Society]] |access-date=28 February 2015}}</ref> Dragonflies can travel at 100 body-lengths per second in forward flight, and three lengths per second backwards.<ref name="UCMP-Berkeley">{{cite web |title=Introduction to the Odonata |url=http://www.ucmp.berkeley.edu/arthropoda/uniramia/odonatoida.html |publisher=UCMP Berkeley |access-date=24 February 2015}}</ref>

==== Motion camouflage ====

{{Further|Motion camouflage}}

[[File:Motion Camouflage Principle.svg|thumb|upright=1.5|The principle of [[motion camouflage]] as used by fighting dragonflies ]]

In high-speed territorial battles between male [[Australian emperor]]s (''Hemianax papuensis''), the fighting dragonflies adjust their flight paths to appear stationary to their rivals, minimizing the chance of being detected as they approach.{{efn|This is not to say that other species may not use the same technique, only that this species has been studied.}}<ref name="NatureNews">{{cite journal | url=http://www.nature.com/news/2003/030605/full/news030602-10.html | title=Nature News | publisher=Nature.com | journal=Dragonfly Flight Tricks the Eye | date=June 5, 2003 | access-date=January 16, 2012 | author=Hopkin, Michael| doi=10.1038/news030602-10 }}</ref><ref name="Mizutani">{{cite journal |last1=Mizutani |first1=A. K. |last2=Chahl |first2=J. S. |last3=Srinivasan |first3=M. V. | date=June 5, 2003 | title=Insect behaviour: Motion camouflage in dragonflies | journal=Nature | volume=65 | issue=423 | pages=604 | doi=10.1038/423604a| pmid=12789327 | bibcode=2003Natur.423..604M | s2cid=52871328 | doi-access=free }}</ref> To achieve the effect, the attacking dragonfly flies towards his rival, choosing his path to remain on a line between the rival and the start of his attack path. The attacker thus [[looming|looms]] larger as he closes on the rival, but does not otherwise appear to move. Researchers found that six of 15 encounters involved [[motion camouflage]].<ref name="Glendinning">{{cite journal | date=27 January 2004 | author=Glendinning, Paul | title=The mathematics of motion camouflage | journal=Proceedings of the Royal Society of London. Series B: Biological Sciences | pmc=1691618 | pmid=15129957 | doi=10.1098/rspb.2003.2622 | volume=271 |issue = 1538| pages=477–81}}</ref>

=== Temperature control ===

The flight muscles need to be kept at a suitable temperature for the dragonfly to be able to fly. Being [[Ectotherm|cold-blooded]], they can raise their temperature by basking in the sun. Early in the morning, they may choose to perch in a vertical position with the wings outstretched, while in the middle of the day, a horizontal stance may be chosen. Another method of warming up used by some larger dragonflies is wing-whirring, a rapid vibration of the wings that causes heat to be generated in the flight muscles. The [[green darner]] (''Anax junius'') is known for its long-distance migrations, and often resorts to wing-whirring before dawn to enable it to make an early start.{{sfn|Berger|2004|pp=44–46}}

Becoming too hot is another hazard, and a sunny or shady position for perching can be selected according to the ambient temperature. Some species have dark patches on the wings which can provide shade for the body, and a few use the [[obelisk posture]] to avoid overheating. This behaviour involves doing a "[[handstand]]", perching with the body raised and the abdomen pointing towards the sun, thus minimising the amount of solar radiation received. On a hot day, dragonflies sometimes adjust their body temperature by skimming over a water surface and briefly touching it, often three times in quick succession. This may also help to avoid desiccation.{{sfn|Berger|2004|pp=44–46}}

=== Feeding ===

[[File:Gomphus vulgatissimus with a prey 002.jpg|thumb|Common clubtail, ''[[Gomphus vulgatissimus]]'', with prey]]

Adult dragonflies hunt on the wing using their exceptionally acute eyesight and strong, agile flight.{{sfn|Trueman|Rowe|2009|page=Life Cycle and Behavior}} They are almost exclusively carnivorous, eating a wide variety of insects ranging from small [[midge]]s and [[mosquito]]es to [[Butterfly|butterflies]], [[moth]]s, [[Damselfly|damselflies]], and smaller dragonflies.<ref name="FAQ"/> A large prey item is subdued by being bitten on the head and is carried by the legs to a perch. Here, the wings are discarded and the prey usually ingested head first.{{sfn|Berger|2004|p=31}} A dragonfly may consume as much as a fifth of its body weight in prey per day.{{sfn|Powell|1999|page=12}} Dragonflies are also some of the [[Hunting_success|most efficient hunters]], catching up to 95% of the prey they pursue.<ref>{{Cite journal|author1=Combes, S.A. |author2=Rundle, D.E. |author3=Iwasaki, J.M. |author4=Crall, J.D. |year=2012|title=Linking biomechanics and ecology through predator–prey interactions: flight performance of dragonflies and their prey|journal=Journal of Experimental Biology |volume=215 |issue=6|pages=903–913 |doi=10.1242/jeb.059394 |pmid=22357584|doi-access=free |bibcode=2012JExpB.215..903C }}</ref>

The nymphs are voracious predators, eating most living things that are smaller than they are. Their staple diet is mostly [[Chironomidae|bloodworms]] and other insect larvae, but they also feed on [[tadpole]]s and small fish.<ref name="FAQ"/> A few species, especially those that live in temporary waters, are likely to leave the water to feed. Nymphs of ''[[Cordulegaster bidentata]]'' sometimes hunt small arthropods on the ground at night, while some species in the ''[[Anax (dragonfly)|Anax]]'' genus have even been observed leaping out of the water to attack and kill full-grown tree frogs.<ref name=diversity /><ref>{{Cite journal|last1=Linares|first1=Antonio Meira|last2=Maciel-Junior|first2=Jose Amantino Horta|last3=de Mello|first3=Humberto Espirito Santo|last4=Leite|first4=Felipe Sa Fortes|date=30 April 2016|title=First report on predation of adult anurans by Odonata larvae|url=http://www.salamandra-journal.com/index.php/home/contents/2016-vol-52/434-linares-a-m-j-a-h-maciel-junior-h-e-s-de-mello-f-s-f-leite/file|journal=Salamandra|volume=52|issue=1|pages=42–44|access-date=20 December 2019|archive-date=24 December 2019|archive-url=https://web.archive.org/web/20191224061849/http://www.salamandra-journal.com/index.php/home/contents/2016-vol-52/434-linares-a-m-j-a-h-maciel-junior-h-e-s-de-mello-f-s-f-leite/file|url-status=dead}}</ref>

=== Eyesight ===

Dragonfly vision is thought to be like slow motion for humans. Dragonflies see faster than humans do; they see around 200 images per second.<ref>{{Cite web |last= |title=Dragonflies see the world in slow motion |url=https://www.bbc.com/reel/video/p035dt53/dragonflies-see-the-world-in-slow-motion |access-date=2023-08-11 |website=BBC Reel |language=en}}</ref> A dragonfly can see in 360 degrees, and nearly 80 percent of the insect's brain is dedicated to its sight.<ref>{{Cite web |title=The Symbolism, Biology and Lore of Dragonflies {{!}} The Dragonfly Foundation |url=https://dragonfly.org/the-symbolism-biology-and-lore-of-dragonflies/ |access-date=2023-08-11 |language=en-US}}</ref>