Editing Dragonfly (section)

=== 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>