Editing Damselfly

{{Short description|Suborder of insects}}
{{Good article}}
{{Automatic taxobox
| name = Damselfly
| fossil_range = {{fossilrange/linked|Kimmeridgian|Recent}}
| image = Beautiful demoiselle (Calopteryx virgo) male 3.jpg
| image_caption = Male beautiful demoiselle <br />(''[[Calopteryx virgo]]'')
| image2 = Ischnura_heterosticta02.jpg
| image2_caption = Female bluetail damselfly <br/>(''[[Ischnura heterosticta]]'')
| taxon = Zygoptera
| authority = [[Edmond de Selys Longschamps|Selys]], 1854<ref name="Selys 1854">{{Cite book|url=https://www.biodiversitylibrary.org/page/39812054|title=Monographie des caloptérygines|language=fr|last=Selys-Longchamps|first=E.|publisher=C. Muquardt|year=1854|location=Brussels and Leipzig|pages=1–291 [2]|doi=10.5962/bhl.title.60461|hdl=2027/hvd.32044107312183}}</ref>
| subdivision_ranks = Superfamilies
| subdivision = * [[Calopterygoidea]]
** [[Calopterygidae]] – demoiselles
** [[Chlorocyphidae]] – jewels
** [[Dicteriadidae]] – barelegs
** [[Euphaeidae]] – odalisques
** [[Lestoideidae]] - bluestreaks
** [[Polythoridae]] – bannerwings
** †[[Zacallitidae]]
* [[Coenagrionoidea]]
** [[Coenagrionidae]] – pond damselflies
** [[Isostictidae]] – narrow-wings
** [[Platycnemididae]] – white-legged damselflies
** [[Pseudostigmatidae]] – forest giants<!--**-->
* [[Lestoidea (superfamily)|Lestoidea]]
** [[Hemiphlebiidae]] – ancient greenling
** [[Lestidae]] – spreadwings
** [[Perilestidae]] – shortwings
** [[Synlestidae]] – sylphs<!--**--> 
* [[Platystictoidea]]
** [[Platystictidae]] – shadowdamsels
}}

'''Damselflies''' are [[flying insect]]s of the suborder '''Zygoptera''' in the order [[Odonata]]. They are similar to [[dragonflies]] (which constitute the other odonatan suborder, [[Epiprocta]]) but are usually smaller and have slimmer bodies. Most species fold the wings along the body when at rest, unlike dragonflies which hold the wings flat and away from the body. Damselflies have existed since the [[Late Jurassic]],<ref name=Jurassic/> and are found on every continent except [[Antarctica]].

All damselflies are [[predatory insect]]s: both [[nymph (biology)|nymph]]s and adults actively hunt and eat other insects. The nymphs are aquatic, with different species living in a variety of [[freshwater ecosystem|freshwater habitat]]s including acidic [[bog]]s, [[pond]]s, [[lake]]s and [[river]]s. The nymphs [[moult]] repeatedly, at the last moult climbing out of the water to undergo [[metamorphosis]]. The skin splits down the back, they emerge and inflate their wings and abdomen to gain their adult form. Their presence on a body of water indicates that it is relatively unpolluted, but their dependence on freshwater makes them vulnerable to damage to their [[wetland]] habitats.

Some species of damselfly have elaborate [[mating|courtship]] behaviours. Many species are [[sexually dimorphic]], the males often being more brightly coloured than the females. Like dragonflies, they reproduce using indirect [[insemination]] and delayed [[fertilisation]]. A mating pair form a shape known as a "heart" or "wheel", the male clasping the female at the back of the head, the female curling her abdomen down to pick up sperm from secondary genitalia at the base of the male's abdomen. The pair often remain together with the male still clasping the female while she lays eggs within the tissue of plants in or near water using a robust [[ovipositor]].

[[Artificial fly|Artificial fishing flies]] that mimic damselfly nymphs are used in wet-[[fly fishing]]. Damselflies are sometimes represented in personal jewellery such as brooches.

== Classification ==
The Zygoptera are an ancient group, with the earliest fossils dating to the [[Kimmeridgian]] age of the [[Late Jurassic]], around 152&nbsp;million years ago.<ref name=Jurassic>{{cite journal |author=Bechly, G. |year=2019 |title=New fossil Odonata from the Upper Jurassic of Bavaria with a new fossil calibration point for Zygoptera |journal=Palaeoentomology |volume=2 |issue=6 |pages=618–632 |doi=10.11646/palaeoentomology.2.6.13 |bibcode=2019Plegy...2..618B |s2cid=210159976 }}</ref> Well-preserved [[Eocene]] damselfly larvae and exuviae are known from fossils preserved in [[amber]] in the Baltic region.<ref>{{cite journal |last1=Bechly |first1=Günter |last2=Wichard |first2=Wilfried |title=Damselfly and dragonfly nymphs in Eocene Baltic amber (Insecta: Odonata), with aspects of their palaeobiology |journal=Palaeodiversity |date=30 December 2008 |volume=1 |pages=37–73 |url=http://www.palaeodiversity.org/pdf/01/Palaeodiversity_1_03_037-074.pdf |access-date=16 March 2015 |archive-date=2 April 2015 |archive-url=https://web.archive.org/web/20150402121339/http://www.palaeodiversity.org/pdf/01/Palaeodiversity_1_03_037-074.pdf |url-status=dead }}</ref>

Molecular analysis in 2021 confirms that most of the traditional families are [[monophyletic]], but shows that the [[Amphipterygidae]], [[Megapodagrionidae]] and [[Protoneuridae]] are [[paraphyletic]] and will need to be reorganised. The Protoneuridae in particular is shown to be composed of six clades from five families. The result so far is 27 damselfly families, with seven more likely to be created. The discovered [[clade]]s did not agree well with traditional characteristics used to classify living and fossil Zygoptera such as wing venation, so fossil taxa will need to be revisited. The results of the analysis are show in the phylogenetic tree shown below, with the seven new or ressurrected families marked with an asterisk:<!--<ref name=Dijkstra2013>{{cite journal |last1=Dijkstra |first1=Klaas-Douwe B. |last2=Kalkman |first2=Vincent J. |last3=Dow |first3=Rory A. |last4=Stokvis |first4=Frank R. |last5=van Tol |first5=Jan |title=Redefining the damselfly families: a comprehensive molecular phylogeny of Zygoptera (Odonata)|journal=Systematic Entomology |volume=39 |issue=1 |pages=68–96 |year=2013 |doi=10.1111/syen.12035 |url=http://www.repository.naturalis.nl/document/634681 |doi-access=free }}</ref> (probably now obsolete given Bybee et al 2021)--><ref name="Bybee 2021">{{cite journal | last1=Bybee | first1=Seth M. | last2=Kalkman | first2=Vincent J. | last3=Erickson | first3=Robert J. | last4=Frandsen | first4=Paul B. | last5=Breinholt | first5=Jesse W. | last6=Suvorov | first6=Anton | last7=Dijkstra | first7=Klaas-Douwe B. | last8=Cordero-Rivera | first8=Adolfo | last9=Skevington | first9=Jeffrey H. | last10=Abbott | first10=John C. | last11=Sanchez Herrera | first11=Melissa | last12=Lemmon | first12=Alan R. | last13=Moriarty Lemmon | first13=Emily | last14=Ware | first14=Jessica L. |display-authors=3 | title=Phylogeny and classification of Odonata using targeted genomics | journal=Molecular Phylogenetics and Evolution | publisher=Elsevier BV | volume=160 | year=2021 | issn=1055-7903 | doi=10.1016/j.ympev.2021.107115 | page=107115| doi-access=free | pmid=33609713 | bibcode=2021MolPE.16007115B | hdl=11093/2768 | hdl-access=free }}</ref>

{{clade |style=font-size:85%;line-height:85%
|grouplabel1={{clade labels |label1="Calopterygoidea" |top1=50% }}
|label1= Zygoptera
|1={{clade
   |label1=[[Lestoidea (superfamily)|Lestoidea]]
   |1={{clade
      |1=[[Hemiphlebiidae]] (ancient greenling)
      |2={{clade
         |1={{clade
             |1=[[Perilestidae]] (shortwings)
             |2=[[Synlestidae]] (sylphs)
             }}
         |2=[[Lestidae]] (spreadwings)
         }}
      }}
   |2={{clade
      |1={{clade
         |label1=[[Platystictoidea]]
         |1=[[Platystictidae]] (shadowdamsels)
         }}
      |2={{clade
         |label1x="Calopterygoidea" Group 1 |bar1=red
         |1=[[Priscagrion|Priscagrionidae]]*
         |2={{clade
            |label1x="Calopterygoidea" Group 2 |bar1=red
            |1={{clade
               |1=[[Philogeniidae]]
               |2={{clade
                  |1={{clade
                     |1=[[Tatocnemididae]]*
                     |2={{clade
                        |1=[[Pentaphlebiidae]]
                        |2=[[Protolestidae]]*
                        }}
                     }}
                  |2={{clade     
                     |1={{clade
                        |1=[[Mesagrionidae]]*
                        |2={{clade
                           |1=[[Dicteriadidae]] (barelegs)
                           |2=[[Hypolestidae]]
                           }}
                        }}
                     |2={{clade
                        |1=[[Heteragrionidae]]
                        |2=[[Polythoridae]] (bannerwings)
                        }}
                     }}
                  }}
               }}
            |2={{clade
               |label1x="Calopterygoidea" Group 3 |bar1=red
               |1={{clade
                  |1={{clade
                     |1=[[Mesopodagrionidae]]*
                     |2=[[Amanipodagrionidae]]*
                     }}
                  |2={{clade
                     |1={{clade
                        |1=[[Pseudolestidae]]
                        |2={{clade
                           |1=[[Lestoideidae]] (bluestreaks)
                           |2=[[Euphaeidae]] (odalisques)
                           }}
                        }}
                     |2={{clade
                        |1={{clade
                           |1=[[Devadattidae]]
                           |2=[[Amphipterygidae]]
                           }}
                        |2={{clade
                           |1=[[Thaumatoneuridae]]
                           |2=[[Rhipidolestidae]]*
                           }}
                        }}
                     }}
                  }}
               |2={{clade
                  |label1x="Calopterygoidea" Group 4 |bar1=red
                  |1={{clade
                     |1={{clade
                        |1=[[Philogangidae]]
                        |2=[[Philosinidae]]
                        }}
                     |2={{clade
                        |1={{clade
                           |1=[[Megapodagrionidae]]
                           |2=[[Argiolestidae]]
                           }}
                        |2={{clade
                           |1=[[Chlorocyphidae]] (jewels)
                           |2=[[Calopterygidae]] (demoiselles)
                           }}
                        }}
                     }}
                  |label2=[[Coenagrionoidea]]
                  |2={{clade
                     |1=[[Isostictidae]] (narrow-wings)
                     |2={{clade
                        |1=[[Platycnemididae]] (white-legged damselflies)
                        |2=[[Coenagrionidae]] (inc. [[Pseudostigmatidae]]) (pond damselflies)
                        }}
                     }}
                  }}
               }}
            }}
         }}
      }}
   }}
}}

==General description==
[[File:Pseudagrion microcephalum wing 0117.svg|thumb|right|Illustration of damselfly wing. Both fore and hind wings are similar.]]
[[File:Pseudagrion caffrum abdomen detail.jpg|thumb|Terminal segments of the abdomen of a male damselfly (''[[Pseudagrion caffrum]]'') showing segments 8–10 (S8, S9, S10), the upper or superior appendages or cerci (c) and the inferior appendages or paraprocts (p)]]
[[File:Blue Damselfly Head GrantPeier.jpg|alt=Damselfly head|thumb|Damselfly head displaying [[compound eye]]s, [[Simple eye in invertebrates|ocelli]], [[Antenna (biology)|antennae]], and [[Insect mouthparts|mouth structures]]]]
[[File:Calopteryx splendens qtl7.jpg|thumb|Male (left) and female of the banded demoiselle, ''[[Calopteryx splendens]]'', showing their [[sexual dimorphism|differently coloured]] wings]]

The general body plan of a damselfly is similar to that of a dragonfly. The [[Eye#Compound eyes|compound eyes]] are large but are more widely separated and relatively smaller than those of a dragonfly. Above the eyes is the frons or forehead, below this the clypeus, and on the lower lip or labium, an extensible organ used in the capture of [[Predation|prey]]. The top of the head bears three simple eyes ([[ocelli]]), which may measure light intensity, and a tiny pair of [[Antenna (biology)|antennae]] that serve no olfactory function but may measure air speed.<ref name=Paulson2011>{{cite book |author=Paulson, Dennis |title=Dragonflies and Damselflies of the East |url=https://books.google.com/books?id=dTpjGOiHwNkC |year=2011 |publisher=Princeton University Press |isbn=978-1-4008-3966-7 |pages=10–32}}</ref> Many species are [[sexual dimorphism|sexually dimorphic]]; the males are often brightly coloured and distinctive, while the females are plainer, [[camouflage|cryptically]] coloured, and harder to identify to species. For example, in ''[[Coenagrion]]'', the Eurasian bluets, the males are bright blue with black markings, while the females are usually predominantly green or brown with black.{{sfn|Dijkstra|2006|pages=20, 104}} A few dimorphic species show female-limited polymorphism, the females being in two forms, one form distinct and the other with the patterning as in males. The ones that look like males, andromorphs, are usually under a third of the female population but the proportion can rise significantly and a theory that explains this response suggests that it helps overcome harassment by males.<ref>{{cite journal|title=A dynamical model of sexual harassment in damselflies and its implications for female-limited polymorphism|first1=Hans Van|last1=Gossum|first2=Thomas N.|last2=Sherratt| journal=Ecological Modelling|volume=210|issue=1–2|year=2008|pages=212–220|doi=10.1016/j.ecolmodel.2007.07.023|bibcode=2008EcMod.210..212V }}</ref> Some Coenagrionid damselflies show male-limited polymorphism, an even less understood phenomenon.<ref>{{cite book|chapter=The evolution of sex-limited colour polymorphism|first1=Hans Van|last1=Gossum|first2=Tom N. |last2=Sherratt|first3=Adolfo|last3=Cordero-Rivera|pages=219–229|title=Dragonflies and Damselflies. Model organisms for ecological and evolutionary research|editor=Cordoba-Aguilar, Alex|publisher=Oxford University Press|year=2008|isbn=9780199230693|chapter-url=https://books.google.com/books?id=IaAUDAAAQBAJ}}</ref>

In general, damselflies are smaller than dragonflies, the smallest being members of the genus ''[[Agriocnemis]]'' (wisps).<ref>{{cite journal |last1=Kipping |first1=Jens |last2=Martens |first2=Andreas |last3=Suhling |first3=Frank |title=Africa's smallest damselfly – a new ''Agriocnemis'' from Namibia |journal=Organisms Diversity & Evolution |date=2012 |doi=10.1007/s13127-012-0084-4 |volume=12 |issue=3 |pages=301–306|s2cid=13356379 }}</ref> However, members of the [[Pseudostigmatidae]] (helicopter damselflies or forest giants) are exceptionally large for the group, with wingspans as much as {{convert|19|cm|in|abbr=on}} in ''[[Megaloprepus]]''<ref>{{cite journal| last = Groenevelda | first = Linn F. |author2=Viola Clausnitzerb |author3=Heike Hadrysa | title = Convergent Evolution of Gigantism in Damselflies of Africa and South America? Evidence from Nuclear and Mitochondrial Sequence Data | journal = Molecular Phylogenetics and Evolution | volume = 42 | issue = 2 | pages = 339–46 | year = 2007 | doi = 10.1016/j.ympev.2006.05.040 | pmid = 16945555| bibcode = 2007MolPE..42..339G }}</ref> and body length up to {{convert|13|cm|in|abbr=on}} in ''[[Pseudostigma aberrans]]''.<ref>{{cite journal| last = Hedström | first = Ingemar |author2=Göran Sahlén | title = A key to the adult Costa Rican "helicopter" damselflies (Odonata: Pseudostigmatidae) with notes on their phenology and life zone preferences | journal = Rev. Biol. Trop. | volume = 49 | issue = 3–4 | pages = 1037–1056 | year = 2001 | url = http://www.scielo.sa.cr/scielo.php?pid=S0034-77442001000300024&script=sci_arttext | pmid = 12189786 }}</ref>

The first [[Thorax (insect anatomy)|thoracic]] segment is the prothorax, bearing the front pair of legs. The joint between head and prothorax is slender and flexible, which enables the damselfly to swivel its head and to manoeuvre more freely when flying. The remaining thoracic segments are the fused mesothorax and metathorax (together termed the [[Thorax (insect anatomy)|synthorax]]), each with a pair of wings and a pair of legs. A dark stripe known as the humeral stripe runs from the base of the front wings to the second pair of legs, and just in front of this is the pale-coloured, antehumeral stripe.<ref name=Paulson2011/>

The forewings and hindwings are similar in appearance and are membranous, being strengthened and supported by longitudinal veins that are linked by many cross-veins and that are filled with [[haemolymph]].<ref name=Silsby>{{cite book |author=Silsby, Jill |title=Dragonflies of the World |url=https://books.google.com/books?id=ddzwJiuRP48C&pg=PA9|year=2001 |publisher=Csiro Publishing |isbn=978-0-643-10249-1 |page=9}}</ref> Species markers include quadrangular markings on the wings known as the [[pterostigma]] or stigma, and in almost all species, there is a [[nodus]] near the leading edge. The thorax houses the flight muscles.<ref name=Paulson2011/> Many damselflies (e.g. Lestidae, Platycnemidae, Coenagrionidae) have clear wings, but some (Calopterygidae, Euphaeidae) have coloured wings, whether uniformly suffused with colour or boldly marked with a coloured patch. In species such as the banded demoiselle, ''[[Calopteryx splendens]]'' the males have both a darker green body and large dark violet-blue patches on all four wings, which flicker conspicuously in their aerial courtship dances; the females have pale translucent greenish wings.{{sfn|Dijkstra|2006|pages=23, 65–67}}

The abdomen is long and slender and consists of ten segments. The secondary genitalia in males are on the undersides of segments two and three and are conspicuous, making it easy to tell the sex of the damselfly when viewed from the side. The female genital opening is on the underside between segments eight and nine. It may be covered by a subgenital plate, or extended into a complex ovipositor that helps them lay eggs within plant tissue. The tenth segment in both sexes bears [[Cercus|cerci]] and in males, its underside bears a pair of paraprocts.<ref name=Paulson2011/>

Damselflies (except spreadwings, [[Lestidae]]) rest their wings together, above their bodies, whereas dragonflies rest with their wings spread diametrically apart; the spreadwings rest with their wings slightly apart. Damselflies have slenderer bodies than dragonflies, and their eyes do not overlap. Damselfly nymphs differ from dragonflies nymphs in that the [[epiproct]] and pair of [[paraproct]]s at the tip of their abdomen has been modified into caudal gills, in addition to being able to absorb oxygen through the wall of their rectum, whereas dragonflies breathe through internal rectal gills only.<ref>[http://assets.press.princeton.edu/chapters/i7940.pdf Dragonflies and Damselflies of Texas and the South-Central United States: Texas, Louisiana, Arkansas, Oklahoma, and New Mexico - Princeton University]</ref><ref>[https://books.google.com/books?id=QjgHAd_SjoAC&dq=gills+zygopterous+epiproct+paraprocts&pg=PA99 Physiology of Insects]</ref> Damselfly nymphs swim by fish-like undulations, the gills functioning like a tail. Dragonfly nymphs can forcibly expel water in their rectum for rapid escape.<ref name=btj>{{cite book|pages=187–201|title=Study of Insects|edition=6|first1=Donald J.|last1=Borror|first2=Charles A.|last2=Triplehorn|first3=Norman F.|last3=Triplehorn|place=Philadelphia|publisher=Saunders College Publishing}}</ref>

==Distribution and diversity==
Odonates are found on all the continents except Antarctica.<ref name=Nilsson>{{cite book|author=Nilsson, Anders |title=Aquatic insects of North Europe: A taxonomic handbook |url=https://books.google.com/books?id=mlAgAQAAMAAJ |year=1997 |publisher=Apollo Books |isbn=978-87-88757-07-1 |page=14}}</ref> Although some species of dragonfly have wide distributions, damselflies tend to have smaller ranges. Most odonates breed in fresh-water; a few damselflies in the family Caenagrionidae breed in brackish water (and a single dragonfly species breeds in seawater).<ref>{{cite journal|title=Observations and Experiments on Dragon-Flies in Brackish Water |first=Raymond C.|last= Osburn |journal=The American Naturalist|volume=40|issue=474|year= 1906|pages= 395–399|doi=10.1086/278632 |url=https://zenodo.org/record/1431341|doi-access=free|bibcode=1906ANat...40..395O }}</ref><ref>{{cite journal|title=Adaptations of Nymphs of a Marine Dragonfly, Erythrodiplax berenice, to Wide Variations in Salinity|first=William A. |last=Dunson|journal=Physiological Zoology|volume=53|issue=4|year=1980|pages=445–452|doi=10.1086/physzool.53.4.30157882 |s2cid=87698039 }}</ref> Dragonflies are more affected by pollution than are damselflies. The presence of odonates indicates that an ecosystem is of good quality. The most species-rich environments have a range of suitable microhabitats, providing suitable water bodies for breeding.<ref name=UCMP>{{cite web |title=Introduction to the Odonata |url=http://www.ucmp.berkeley.edu/arthropoda/uniramia/odonatoida.html |publisher=UCMP Berkeley |access-date=13 March 2015 |archive-url=https://web.archive.org/web/20170827225730/http://www.ucmp.berkeley.edu/arthropoda/uniramia/odonatoida.html |archive-date=27 August 2017 |url-status=dead }}</ref><ref name=diversity />

Although most damselflies live out their lives within a short distance of where they were hatched, some species, and some individuals within species, disperse more widely. [[Ischnura|Forktails]] in the family [[Coenagrionidae]] seem particularly prone to do this, large male [[boreal bluet]]s (''Enallagma boreale'') in British Columbia often migrating, while smaller ones do not.<ref name=Acorn/> These are known to leave their waterside habitats, flying upwards till lost from view, and presumably being dispersed to far off places by the stronger winds found at high altitudes.<ref name=Acorn/> In this way they may appear in a locality where no damselflies were to be seen the day before. [[Rambur's forktail]] (''Ischnura ramburii'') has been found, for example, on [[Oil platform|oil rigs]] far out in the [[Gulf of Mexico]].<ref name=Paulson2011/>

The distribution and diversity of damselfly species in the [[biogeographical]] regions is summarized here. (There are no damselflies in the [[Antarctic]].) Note that some species are widespread and occur in multiple regions.<ref name=diversity />

{| class="wikitable sortable collapsible collapsed"
|- style="font-size:86%"
! Family
! [[Indomalaya|Oriental]]
! [[Neotropical]]
! [[Australasia]]n
! [[Afrotropical]]
! [[Palaearctic]]
! [[Nearctic]]
! [[Oceania|Pacific]]
! World 
|-
| [[Hemiphlebiidae]]||||||1||||||||||1
|-
| [[Lestidae]]||40||42||29||17||18||18||3||151
|-
| [[Perilestidae]]||||19||||||||||||19
|-
| [[Synlestidae]]||18||1||8||11||6||||||39
|-
| [[Platystictidae]]||136||43||44||||||1||1||224
|-
| [[Amphipterygidae]]||||4||||||||||||4
|-
| [[Argiolestidae]]||10||||73||19||||||6||108
|-
| [[Calopterygidae]]||66||68||5||20||37||8||||185
|-
| [[Chlorocyphidae]]||86||||17||42||3||||||144
|-
| [[Devadattidae]]||6||||||||||||||6
|-
| [[Dicteriadidae]]||||2||||||||||||2
|-
| [[Euphaeidae]]||65||||1||||11||||||68
|-
| [[Heteragrionidae]]||||51||||||||||||51
|-
| [[Hypolestidae]]||||2||||||||||||2
|-
| [[Lestoideidae]]||||||9||||||||||9
|-
| [[Megapodagrionidae]]||||29||||||||||||29
|-
| [[Pentaphlebiidae]]||||||||2||||||||2
|-
| [[Philogangidae]]||4||||||||2||||||4
|-
| [[Philogeniidae]]||||39||||||||||||39
|-
| [[Philosinidae]]||12||||||||||||||12
|-
| [[Polythoridae]]||||59||||||||||||59
|-
| [[Pseudolestidae]]||1||||||||||||||1
|-
| [[Rimanellidae]]||||1||||||||||||1
|-
| [[Thaumatoneuridae]]||||5||||||||||||5
|-
| ''[[Incertae sedis]]''||25||11||||19||9||||||61
|-
| [[Coenagrionidae]]||193||554||152||202||96||103||91||1266
|-
| [[Isostictidae]]||||||41||||||||||46
|-
| [[Platycnemididae]]||199||||122||70||22||||||404
|-
|}
Overall, there are about 2942 extant species of damselflies placed in 309 genera.<ref name=diversity>{{cite book |title=Ecology and general biology. Thorp and Covich's Freshwater Invertebrates |edition=4 |publisher=Academic Press |editor=Thorp, James |editor2=D. Christopher Rogers |isbn=978-0-12-385026-3 |author1=Suhling, F. |author2=Sahlén, G. |author3=Gorb, S. |author4=Kalkman, V.J. |author5=Dijkstra, K-D.B. |author6=van Tol, J. |year=2015 |chapter=Order Odonata |pages= 893–932}}</ref>

== Biology ==
[[File:Blue Damselflies sparkling over Kew pond.webm|thumb|Blue damselflies swarming over pond in [[Kew Gardens]]. Some pairs (blue male in front) are seen.]]
[[File:Damselfly catch Updated.webm|thumb|right|thumbtime=0|[[Ischnura perparva|Western forktail damselfly]] attempting on-the-fly catches. Each repeated in slow motion. The second prey landed, escaping capture. Finally closeup devouring medium sized fly.]]

[[File:Damselfly eating Crane fly.jpg|left|thumb|Damselfly eating a Crane fly]]
Adult damselflies catch and eat flies, mosquitoes, and other small insects. Often they hover among grasses and low vegetation, picking prey off stems and leaves with their spiny legs (unlike dragonflies which prefer catching flying prey).<ref name=Acorn/><ref>[https://books.google.com/books?id=Ygoyg1grhJwC&dq=dragonflies+generally+capture+their+prey+while+in+flight&pg=PA8 Dragonflies and Damselflies of Georgia and the Southeast]</ref> Although predominantly using vision to locate their prey, adults may also make use of olfactory cues.<ref>{{cite journal|title= First evidence of the use of olfaction in Odonata behaviour| journal=Journal of Insect Physiology|volume=62|year=2014|pages=26–31|first1=Silvana|last1=Piersanti|first2= Francesca|last2= Frati|first3=Eric|last3= Conti|first4= Elda|last4=Gaino|first5=Manuela|last5= Rebora|first6= Gianandrea |last6=Salerno|doi=10.1016/j.jinsphys.2014.01.006| pmid=24486162| bibcode=2014JInsP..62...26P}}</ref> No species are known to hunt at night, but some are crepuscular, perhaps taking advantage of newly hatched flies and other aquatic insects at a time when larger dragonflies are roosting.<ref name=Heckman/> In tropical South America, helicopter damselflies ([[Pseudostigmatidae]]) feed on [[spider]]s, hovering near an orb web and plucking the spider, or its entangled prey, from the web.<ref>{{cite journal |author1=Ingley, Spencer J. |author2=Bybee, Seth M. |author3=Tennessen, Kenneth J. |author4=Whiting, Michael F. |author5=Branham, Marc A. |year=2012 |title=Life on the fly: phylogenetics and evolution of the helicopter damselflies (Odonata, Pseudostigmatidae) |journal=Zoologica Scripta |volume=41 |issue=6 |pages=637–650 |doi=10.1111/j.1463-6409.2012.00555.x |s2cid=82370392 }}</ref> There are few pools and lakes in these habitats, and these damselflies breed in temporary water bodies in holes in trees, the rosettes of [[bromeliad]]s and even the hollow stems of [[bamboo]]s.<ref>{{cite conference | last = Fincke | first = Ola M. | title = Use of Forest and Tree Species, and Dispersal by Giant Damselflies (Pseudostigmatidae): Their Prospects in Fragmented Forests | book-title = Fourth WDA International Symposium of Odonatology, Pontevedra (Spain), July 2005 | editor = Adolfo Cordero Rivera | pages = 103–125 | publisher = Pensoft Publishers | year = 2006 | location = Sofia—Moscow | url = http://faculty-staff.ou.edu/F/Ola.M.Fincke-1/06%20-%20Fincke.pdf | url-status = dead | archive-url = https://web.archive.org/web/20070628043336/http://faculty-staff.ou.edu/F/Ola.M.Fincke-1/06%20-%20Fincke.pdf | archive-date = 2007-06-28 }}</ref>

The nymphs of damselflies have been less researched than their dragonfly counterparts, and many have not even been identified. They choose their prey according to size and seem less able to overpower larger prey than can dragonfly nymphs. The major part of the diet of most species appears to be [[crustacean]]s such as [[Cladocera|water fleas]].<ref name=Heckman/>

===Ecology===
[[File:Panorama of Thursley Common, looking over the bog pools.JPG|thumb|upright=1.7<!--size for very low image-->|Fine damselfly habitat: panorama of [[Thursley Common]], looking over the acid bog pools]]
[[File:The damselfly Platycnemis pennipes washing itself.webm|thumb|Damselfly grooming]]
[[File:Pseudagrion decorum damselfly with water mites.jpg|thumb|Water mites parasitizing ''[[Pseudagrion decorum]]'']]

Damselflies exist in a range of habitats in and around the wetlands needed for their larval development; these include open spaces for finding mates, suitable perches, open aspect, roosting sites, suitable plant species for ovipositing and suitable water quality. Odonates have been used for [[bio-indication]] purposes regarding the quality of the [[ecosystem]]. Different species have different requirements for their larvae with regard to water depth, water movement and pH.<ref name=Allen2009>{{cite book |title=The ecology and conservation of threatened damselflies |last=Allen |first=Katherine |year=2009 |publisher=The Environment Agency |isbn=978-1-84911-093-8 |pages=1–6 }}</ref>
The European [[Enallagma cyathigerum|common blue damselfly]] (''Enallagma cyathigerum'') for example can occur at high densities in [[acid]] waters where fish are absent, such as in bog pools.{{sfn|Dijkstra|2006|page=102}}
The [[scarce blue-tailed damselfly]] (''Ischnura pumilio'') in contrast requires [[alkali|base-rich]] habitats and water with a slow flow-rate. It is found in ditches, quarries, seeps, flushes, marshes and pools. It tolerates high levels of zinc and copper in the sediment but requires suitable emergent plants for egg-laying without the water being choked by plants.<ref name=Allen2009/> Damselflies' dependence on freshwater habitats makes them very vulnerable to damage to wetlands through drainage for agriculture or urban growth.<ref name=Corbet1980>{{cite journal |last1=Corbet |first1=P. S. |title=Biology of Odonata |journal=Annual Review of Entomology |date=1980 |volume=25 |pages=189–217 |doi=10.1146/annurev.en.25.010180.001201 }}</ref>

In the tropics, the helicopter damselfly ''Mecistogaster modesta'' ([[Pseudostigmatidae]]) breeds in [[phytotelmata]], the small bodies of water trapped by [[bromeliad]]s, [[epiphytic]] plants of the [[rainforest]] of northwest [[Costa Rica]], at the high density of some 6000 larvae per hectare in patches of secondary forest.<ref>{{cite journal |last1=Srivastava |first1=Diane S. |last2=Melnychuk |first2=Michael C. |last3=Ngai |first3=Jacqueline T. |s2cid=53603745 |title=Landscape variation in the larval density of a bromeliad-dwelling zygopteran, Mecistogaster modesta (Odonata: Pseudostigmatidae) |journal=International Journal of Odonatology |date=2005 |volume=8 |issue=1 |pages=67–79 |doi=10.1080/13887890.2005.9748244 |bibcode=2005IJOdo...8...67S }}</ref> Another tropical species, the cascade damselfly ''[[Thaumatoneura inopinata]]'' ([[Megapodagrionidae]]), inhabits [[waterfall]]s in Costa Rica and Panama.<ref>{{cite journal|title=Studies on Costa Rican Odonata. V. The waterfall-dwellers: Thaumatoneura imagos and possible male dimorphism|author=Calvert, Philip P.|journal=Entomological News and Proceedings of the Entomological Section|volume=25|issue=8|year=1914|pages=337–348|url= https://archive.org/stream/entomologicalnew25acad#page/n421/mode/2up}}</ref><ref>{{cite iucn |author=Paulson, D. R. |date=2009 |title=''Thaumatoneura inopinata'' |volume=2009 |page=e.T21721A9313826 |doi=10.2305/IUCN.UK.2009-2.RLTS.T21721A9313826.en |access-date=13 November 2021}}{{Dead link|date=August 2019 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

Damselflies, both nymphs and adults, are eaten by a range of [[predators]] including birds, fish, frogs, dragonflies, other damselflies, [[Diving bell spider|water spiders]], [[water beetle]]s, [[Notonectidae|backswimmers]] and [[Belostomatidae|giant water bugs]].<ref name=Acorn>{{cite book|author=Acorn, John|title=Damselflies of Alberta: Flying Neon Toothpicks in the Grass |url=https://archive.org/details/damselfliesofalb00acor |url-access=registration|year=2004 |publisher=University of Alberta |isbn=978-0-88864-419-0|pages=[https://archive.org/details/damselfliesofalb00acor/page/9 9]–15}}</ref>

Damselflies have a variety of internal and external parasites. Particularly prevalent are the [[Gregarinasina|gregarine protozoans]] found in the gut. In a study of the European common blue damselfly, every adult insect was infected at the height of the flying season. When present in large numbers, these parasites can cause death by blocking the gut.<ref name="Acorn" /> Water mites [[Hydrachnidiae|Hydracarina]] are often seen on the outside of both nymphs and adults, and can move from one to the other at metamorphosis.<ref name="Acorn" /> They suck the body fluids and may actually kill young nymphs, but adults are relatively unaffected, it being necessary for the completion of the mite's life cycle that it returns to water, a feat accomplished when the adult damselfly breeds.<ref>{{cite book|author=Proctor, Heather |title=Aquatic Mites from Genes to Communities: From Genes to Communities |url=https://books.google.com/books?id=PoOL_XRi9WsC&pg=PA91 |year=2004 |publisher=Springer Science & Business Media |isbn=978-1-4020-2703-1 |pages=79–84}}</ref>

=== Behaviour ===

[[File:Blue-fronted Dancer (Argia apicalis) (14681891387).jpg|thumb|left|Female blue-fronted dancer]]

Many damselflies have elaborate courtship behaviours. These are designed to show off the male's distinctive characteristics, bright colouring or flying abilities, thus demonstrating his fitness. ''[[Calopteryx (damselfly)|Calopteryx]]'' males will hover in front of a female with alternating fast and slow wingbeats; if she is receptive she will remain perched, otherwise she will fly off. The male [[Calopteryx aequabilis|river jewelwing]] (''Calopteryx aequabilis'') performs display flights in front of the female, fluttering his forewings while keeping his hindwings still, and raising his abdomen to reveal the white spots on his wings.{{sfn|Paulson|2009|page=42}}  ''[[Platycypha]]'' males will hover in front of a female, thrusting their bright white legs forward in front of their heads. Flattened tibia and bright leg colouring are seen in ''[[Platycnemis phasmovolans]]'' and a few other [[Platycnemididae]], including the extinct ''[[Yijenplatycnemis huangi]]''.<ref name="Zheng Nel 2017">{{cite journal |last1=Zheng |first1=Daran |last2=Nel |first2=André |last3=Jarzembowski |first3=Edmund A. |last4=Chang |first4=Su-Chin |last5=Zhang |first5=Haichun |last6=Xia |first6=Fangyuan |last7=Liu |first7=Haoying |last8=Wang |first8=Bo |date=2017 |title=Extreme adaptations for probable visual courtship behaviour in a Cretaceous dancing damselfly |journal=Scientific Reports |volume=7 |issue=1 |pages=44932 |doi=10.1038/srep44932 |issn=2045-2322 |pmc=5357891 |pmid=28317876 |bibcode=2017NatSR...744932Z }}</ref> ''[[Rhinocypha]]'' bobs up and down, often low over fast-flowing forested and shaded streams, displaying its bright-coloured body and wings.<ref name="Silsby 2001 p58"/> Some species (''R. biceriata'', ''R. humeralis'') have a foot waggling behaviour: they thrust a leg forward and vibrate it towards ovipositing females while in flight.<ref name="Orr 1996">{{cite journal |last=Orr |first=A. G. |date=1996 |title=Territorial and courtship displays in Bornean Chlorocyphidae (Zygoptera) |url=https://natuurtijdschriften.nl/pub/592155/OJIOS1996025002002.pdf |journal=Odonatologica |volume=25 |issue=2 |pages=119–141}}</ref> Vibrating the tibia is seen in ''Libellago semiopaca'' despite it lacking bright colouration on the tibia suggesting that foot waggling is a generalized excitary signal in Chlorocyphidae damselflies.<ref name="Orr 1996"/>  Foot waggling has been observed in ''Calopteryx'' sp., ''[[Platycypha fitzsimonsi]]'',<ref name="Robertson 1982">{{cite journal |last=Robertson |first=H. M. |date=1982 |title=Courtship displays and mating behaviour of three species of Chlorocyphida (Zygoptera) |url=https://natuurtijdschriften.nl/pub/591569/OJIOS1982011001007.pdf |journal=Odonatologica |volume=11 |issue=1 |pages=53–58}}</ref> and ''[[Platycypha caligata]]''. Male members of the family [[Protoneuridae]] with vividly coloured wings display these to visiting females.<ref name="Silsby 2001 p58">{{cite book |last=Silsby |first=Jill |title=Dragonflies of the World |url=https://books.google.com/books?id=ddzwJiuRP48C&pg=PA58 |year=2001 |publisher=Csiro Publishing |isbn=978-0-643-10249-1 |pages=58–59}}</ref> [[Ischnura erratica|Swift forktail]] (''Ischnura erratica'') males display to each other with their blue-tipped abdomens raised.{{sfn|Paulson|2009|page=108}}

[[File:Euphaea fraseri-Aralam-2016-10-29-001.jpg|thumb|upright|''[[Euphaea fraseri]]'' males [[Territory (animal)#Resources defended|defend their territory]], with open wings and prominently [[Display (zoology)#Among animals|display]] the iridescent copper markings of the upper hind wing.]]

Other behaviours observed in damselflies include wing-warning, wing-clapping, flights of attrition and abdominal bobbing. Wing-warning is a rapid opening and closing of the wings and is aggressive, while wing-clapping involves a slower opening of the wings followed by a rapid closure, up to eight times in quick succession, and often follows flight; it may serve a thermo-regulatory function.<ref name=Bick>{{cite journal |author1=Bick, George H. |author2=Bick, Juanda C. |year=1961 |title=Demography and Behavior of the Damselfly, ''Argia Apicalis'' (Say), (Odonata: Coenagriidae) |journal=Ecology |volume=46 |issue=4 |pages=461–472 |jstor=1934877 |doi=10.2307/1934877}}</ref> Flights of attrition are engaged in by the [[ebony jewelwing]] (''Calopteryx maculata'') and involve males bouncing around each other while flying laterally and continuing to do so, sometimes over a considerable distance, until one insect is presumably exhausted and gives up.{{sfn|Paulson|2009|page=44}} Characteristics of displays and coloration of males are suggested to be the common cues used by females to choose mates. In at least one species, ''Mnais costalis'', males with more sunlight in their territories had higher wing-beat frequency and were more likely to mate. Females preferred "hotter" males because they would be on warmer territories for egg laying.<ref>{{Cite journal |last1=Tsubaki |first1=Yoshitaka |last2=Samejima |first2=Yuka |last3=Siva-Jothy |first3=Michael T. |date=2010 |title=Damselfly females prefer hot males: higher courtship success in males in sunspots |url=https://doi.org/10.1007/s00265-010-0968-2 |journal=Behavioral Ecology and Sociobiology |language=en |volume=64 |issue=10 |pages=1547–1554 |doi=10.1007/s00265-010-0968-2 |bibcode=2010BEcoS..64.1547T |issn=1432-0762}}</ref>

At night, damselflies usually roost in dense vegetation, perching with the abdomen alongside a stem. If disturbed they will move around to the other side of the stem but will not fly off. Spreadwings fully fold their wings when roosting.<ref name=Paulson2011/> The [[Palaemnema domina|desert shadowdamsel]] (''Palaemnema domina'') aggregates to roost in thick places near streams in the heat of the day. While there it engages in wing-clapping, the exact function of which is unknown.{{sfn|Paulson|2009|page=185}} Some species such as the rubyspot damselfly, ''[[American rubyspot|Hetaerina americana]]'', form night roosting aggregations, with a preponderance of males; this may have an anti-predator function or may be simply the outcome of choosing safe roosting sites.<ref name=Switzer>{{cite journal |last1=Switzer |first1=Paul V.|last2=Grether|first2=Gregory F.|title=Characteristics and Possible Functions of Traditional Night Roosting Aggregations in Rubyspot Damselflies |journal=Behaviour |date=2000 |volume=137 |issue=4|pages=401–416 |url=https://www.eeb.ucla.edu/Faculty/Grether/PDF/Switzer&Grether2000.pdf |doi=10.1163/156853900502141 |s2cid=85986224 }}</ref>

===Reproduction===
Mating in damselflies, as in dragonflies, is a complex, precisely choreographed process involving both indirect insemination and delayed fertilisation.{{sfn|Dijkstra|2006|pages=8–9}}<ref name=Battin>{{cite journal|last1=Battin |first1=Tom |title=The odonate mating system, communication, and sexual selection: A review |journal= Bolletino di Zoologia|date=1993 |volume=60 |issue=4 |pages=353–360 |doi=10.1080/11250009309355839 |doi-access=free }}</ref> The male first 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=Battin/><ref name=Cordero>{{cite book |last1=Cordero-Rivera |first1=Adolfo |last2=Cordoba-Aguilar |first2=Alex |chapter=Selective Forces Propelling Genitalic Evolution in Odonata |year=2010 |page=343 |chapter-url=http://ecoevo.uvigo.es/pdf/2010/2010-Genital%20evolution%20odonata-lq.pdf |title=The Evolution of Primary Sexual Characters in Animals |editor=Leonard, Janet |editor2=Alex Córdoba-Aguilar |publisher=Oxford University Press |access-date=2015-03-16 |archive-date=2015-02-25 |archive-url=https://web.archive.org/web/20150225124220/http://ecoevo.uvigo.es/pdf/2010/2010-Genital%20evolution%20odonata-lq.pdf |url-status=dead }}</ref> The pair fly 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".{{sfn|Berger|2004|p=39|ps=: <q>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'.</q>}} Males may transfer the sperm to their secondary genitalia either before a female is held, in the early stage when the female is held by the legs or after the female is held between the terminal claspers. This can lead to variations in the tandem postures.<ref>{{cite journal|doi=10.1093/aesa/58.4.592|pmid=5834678|title=Sperm Transfer in Damselflies (Odonata: Zygoptera)|journal=Annals of the Entomological Society of America|volume=58|issue=4|pages=592|year=1965|last1=Bick|first1=G. H.|last2=Bick|first2=J. C.}}</ref> The spermatophore may also have nutrition in addition to sperms as a "[[nuptial gift]]".<ref>{{cite book|last1=Cordero Rivera |first1= A|last2=Cordoba-Aguilar |first2=A |year=2010| chapter=Selective forces propelling genitalic evolution in Odonata|editor1=  Leonard J|editor2=Cordoba-Aguilar, A |title=  The evolution of primary characters in animals|publisher= Oxford University Press|place= New York|pages= 332–352}}</ref> Some cases of [[sexual cannibalism]] exist where females (of ''[[Ischnura graellsii]]'') eat males while in copula.<ref>{{cite journal|doi=10.1127/entom.gen/17/1992/17|url=http://ecoevo.uvigo.es/PDF/Entomol_Gener_vol_17_pp_17-20_(1992).pdf|journal=Entomologia Generalis|volume=17|issue=1|year=1992|pages=17–20|title=Sexual Cannibalism in the Damselfly Species Ischnura graellsii (Odonata: Coenagrionidae)|author=Cordero, Adolfo|access-date=2017-04-28|archive-url=https://web.archive.org/web/20130613025042/http://ecoevo.uvigo.es/PDF/Entomol_Gener_vol_17_pp_17-20_%281992%29.pdf|archive-date=2013-06-13|url-status=dead}}</ref>

[[Parthenogenesis]] (reproduction from unfertilised eggs) is exceptional, and has only been recorded in nature in female ''[[Ischnura hastata]]'' on the [[Azores Islands]].<ref name=diversity /><ref>{{cite journal |journal= Heredity |volume=103|issue=5|pages=377–384 |doi=10.1038/hdy.2009.65 |pmid=19513091|year= 2009 |title=Thelytokous parthenogenesis in the damselfly ''Ischnura hastata'' (Odonata, Coenagrionidae): genetic mechanisms and lack of bacterial infection |first1=M. O. |last1=Lorenzo-Carballa |first2= A. |last2=Cordero-Rivera|doi-access=free|bibcode=2009Hered.103..377L }}</ref>

Egg-laying (ovipositing) involves not only the female darting over floating or waterside vegetation to deposit eggs on a suitable substrate, but the male hovering above her, mate-guarding, or in some species continuing to clasp her and flying in tandem. The male attempts to prevent rivals from removing his sperm and inserting their own,<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> a form of [[sperm competition]] (the sperms of the last mated male have the greatest chance of fertilizing the eggs, also known as sperm precedence<ref name=reshcarde>{{cite book|chapter=Odonata (Dragonflies, Damselflies)|author=Tennessen, K.J.|pages=721–729|title=Encyclopedia of Insects|edition=2|editor=Resh, Vincent H. |editor2=Ring T. Cardé|year=2009|publisher=Academic Press}}</ref>) made possible by delayed fertilisation{{sfn|Dijkstra|2006|pages=8–9}}{{sfn|Trueman|Rowe|2009|page=Life Cycle and Behavior}} and driven by [[sexual selection]].<ref name=Battin/><ref name=Cordero/> If successful, a rival male uses his penis to compress or scrape out the sperm inserted previously; this activity takes up much of the time that a copulating pair remain in the heart posture.{{sfn|Berger|2004|p=39|ps=: <q>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'.</q>}} 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/>

<gallery widths="200" heights="175">
File:Ceriagrion cerinorubellum-Kadavoor-2016-04-11-002.jpg|alt=Damselflies holding each other|First stage: ''[[Ceriagrion cerinorubellum]]'' pair with male transferring sperm from the primary to the secondary sex organs
File:Ceriagrion cerinorubellum-Kadavoor-2016-04-11-003.jpg|alt=Mating damselflies in heart position|Second stage: "heart" or "wheel" position, the female receiving sperm from the male secondary sex organ
File:Pseudagrion indicum ovipositing at Kadavoor.jpg|Yellow-striped blue dart, ''[[Pseudagrion indicum]]'', laying eggs; the male (above) continues to hold the female with his claspers.
Hetaerina americana-mating.webm|''[[Hetaerina americana]]'' mating: sperm removal
File:Chalcolestes viridis laying eggs into slits in twig.jpg|Willow emerald, ''[[Chalcolestes viridis]]'', still in tandem, laying eggs into a series of slits in a twig
</gallery>

All damselflies lay their eggs inside plant tissues; those that lay eggs underwater may submerge themselves for 30 minutes at a time, climbing along the stems of aquatic plants and laying eggs at intervals.<ref name=Lawlor>{{cite book |author=Lawlor, 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> For example, the red-eyed damselfly ''[[Erythromma najas]]'' lays eggs, in tandem, into leaves or stems of floating or sometimes emergent plants; in contrast, the scarce bluetail ''[[Ischnura pumilio]]'' oviposits alone, the female choosing mostly emergent grasses and rushes, and laying her eggs in their stems either above or just below the waterline.<ref name="SmallshireSwash2014">{{cite book |last1=Smallshire |first1=Dave |last2=Swash |first2=Andy |title=Britain's Dragonflies: A Field Guide to the Damselflies and Dragonflies of Britain and Ireland: A Field Guide to the Damselflies and Dragonflies of Britain and Ireland |url=https://books.google.com/books?id=jG9UAwAAQBAJ&pg=PA96 |year=2014 |publisher=Princeton University Press |isbn=978-1-4008-5186-7 |pages=94–96}}</ref> The willow emerald ''[[Chalcolestes viridis]]'' (a spreadwing) is unusual in laying eggs only in woody plant tissue, choosing thin twigs of trees that hang over water, and scarring the bark in the process.{{sfn|Dijkstra|2006|page=84}} A possible exception is an apparent instance of [[viviparity|ovo-viviparity]], in which ''[[Heliocypha perforata]]'' was filmed in western China depositing young larvae (presumably hatched from eggs inside the female's body) onto a partly submerged branch of a tree.<ref name=Salindra>{{cite journal|last1=Salindra |first1=H. G. |last2=Dayananda|first2=K. |last3=Kitching |first3=Roger L. |title=Ovo-viviparity in the Odonata? The case of Heliocypha perforata (Zygoptera: Chlorocyphidae) |journal=International Journal of Odonatology|year=2014 |volume=17 |issue=4 |pages=181–185 |doi=10.1080/13887890.2014.959076 |bibcode=2014IJOdo..17..181D |s2cid=83520585 |doi-access=free }}</ref>

Many damselflies are able to produce more than one brood per year ([[voltinism]]); this is negatively correlated with [[latitude]], becoming more common towards the equator, except in the Lestidae.<ref name=Corbet2006>{{cite journal |last1=Corbet |first1=Philip S. |last2=Suhling |first2=Frank |last3=Soendgerath |first3=Dagmar |title=Voltinism of Odonata: a review |journal=International Journal of Odonatology|date=2006|volume=9 |issue=1 |pages=1–44 |url=https://www.researchgate.net/publication/228369286 |doi=10.1080/13887890.2006.9748261|bibcode=2006IJOdo...9....1C |s2cid=55299239 |doi-access=free }}</ref>

===Life cycle===
Damselflies are [[Hemimetabolism|hemimetabolous]] insects that have no pupal stage in their development.<ref>{{cite book|title=A Dictionary of Entomology|url=https://books.google.com/books?id=9IcmCeAjp6cC&pg=PA679 |year=2011 |publisher=CABI |isbn=978-1-84593-542-9 |page=679}}</ref> The female inserts the eggs by means of her ovipositor into slits made in water plants or other underwater [[Substrate (biology)|substrates]] and the larvae, known as naiads or nymphs, are almost all completely aquatic.<ref name=Paulson2011/> Exceptions include the Hawaiian ''[[Megalagrion oahuense]]'' and an unidentified Megapodagrionid from New Caledonia,<ref>{{cite journal |journal=Psyche: A Journal of Entomology |volume=62 |issue=4 |year=1955 |title=A terrestrial damselfly nymph (Medapodarionidae) from New Caledonia |author=Willey, Ruth Lippitt |pages=137–144 |url=http://downloads.hindawi.com/journals/psyche/1955/039831.pdf |doi=10.1155/1955/39831|doi-access=free }}</ref> which are terrestrial in their early stages.<ref name=Carde/> The [[Lestidae|spreadwings]] lay eggs above the waterline late in the year and the eggs overwinter, often covered by snow. In spring they hatch out in the meltwater pools and the nymphs complete their development before these temporary pools dry up.<ref name=Acorn/>

The nymphs are voracious [[Predation|predators]] and feed by means of a flat [[Insect mouthparts#Labium|labium]] (a toothed mouthpart on the lower jaw) that forms the so-called mask; it is rapidly extended to seize and pierce the ''[[Daphnia]]'' (water fleas), [[mosquito]] larvae, and other small aquatic organisms on which damselfly nymphs feed. They breathe by means of three large external, fin-like gills on the tip of the abdomen, and these may also serve for locomotion in the same manner as a fish's tail.<ref name=Paulson2011/> Compared to dragonfly larvae, the nymphs show little variation in form. They tend to be slender and elongate, many having morphological adaptations for holding their position in fast flowing water. They are more sensitive than dragonfly nymphs to oxygen levels and suspended fine particulate matter, and do not bury themselves in the mud.<ref name=Heckman>{{cite book |author=Heckman, Charles W. |title=Encyclopedia of South American Aquatic Insects: Odonata - Zygoptera: Illustrated Keys to Known Families, Genera, and Species in South America |url=https://books.google.com/books?id=PG_td3hm7XoC&pg=PA17 |year=2008 |publisher=Springer |isbn=978-1-4020-8176-7 |pages=17, 31–33}}</ref>

The nymphs proceed through about a dozen moults as they grow. In the later stages, the wing pads become visible. When fully developed, the nymphs climb out of the water and take up a firm stance, the skin on the thorax splits and the adult form wriggles out. This has a soft body at first and hangs or stands on its empty larval case. It pumps haemolymph into its small limp wings, which expand to their full extent. The haemolymph is then pumped back into the abdomen, which also expands fully. The [[exoskeleton]] hardens and the colours become more vivid over the course of the next few days. Most damselflies emerge in daytime, and in cool conditions the process takes several hours. On a hot day, the cuticle hardens rapidly and the adult can be flying away within half an hour.<ref name=Paulson2011/>

<gallery widths="200" heights="200">
File:Blue-tailed damselfly (Ischnura elegans) nymph.jpg|Blue-tailed damselfly (''[[Ischnura elegans]]'') nymph, showing the three tail appendages
File:Damselfly emergence-Aralam-2016-10-29-001.jpg|''[[Prodasineura verticalis]]'' female emerging from the [[exuviae|split skin of the nymph]]
</gallery>

==Conservation==
Conservation of Odonata has usually concentrated on the more iconic suborder Anisoptera, the dragonflies. However, the two suborders largely have the same needs, and what is good for dragonflies is also good for damselflies. The main threats experienced by odonates are the clearance of forests, the pollution of waterways, the lowering of groundwater levels, the damming of rivers for [[Hydroelectricity|hydroelectric schemes]] and the general degradation of wetlands and marshes.<ref name=Moore>{{cite web |url=https://testportals.iucn.org/library/sites/library/files/documents/1997-042.pdf |archive-url=https://web.archive.org/web/20160412200713/https://testportals.iucn.org/library/sites/library/files/documents/1997-042.pdf |url-status=dead |archive-date=12 April 2016 |title=Dragonflies: status survey and conservation action plan |author=Moore, N.W. |year=1997 |publisher=International Union for Conservation of Nature |access-date=17 March 2015 }}</ref> The clearance of tropical rainforests is of importance because the rate of erosion increases, streams and pools dry up and waterways become clogged with silt. The presence of alien species can also have [[unintended consequences]].<ref name=Moore/> In Hawaii, the introduction of the [[mosquitofish]] (''Gambusia affinis'') was effective in controlling mosquitoes but nearly exterminated the island's endemic damselflies.<ref>{{cite journal |author=Gagné, W.C. |year=1981 |title=Status of Hawaii endangered species: insects and land snails |journal=ʻElepaio  |volume=42 |pages=31–36 }}</ref> The ancient greenling ''[[Hemiphlebia mirabilis]]'' has been an important flagship species for conservation action in preserving its habitat in Australia.<ref>{{cite journal|journal=The Victorian Naturalist|volume=124|issue=4|pages= 269–272 |url=http://arrow.latrobe.edu.au:8080/vital/access/manager/Repository/latrobe:24665|title=The Hemiphlebia damselfly Hemiphlebia mirabilis Selys (Odonata, Zygoptera) as a flagship species for aquatic insect conservation in south-eastern Australia|author= New, Timothy Richard}}</ref>

==In culture==

[[Fishing flies]] that mimic damselfly nymphs are sometimes used in wet-fly fishing, where the hook and line are allowed to sink below the surface.<ref>{{cite web |title=Fishing Tips for the Juicebug Damsel Nymph |author=Wada, Wes |url=http://flyfoundry.com/wes-wadas-signature-flies/featured-fly-juicebug-damsel-nymph/fishing-tips-for-the-juicebug-damsel-nymph/ |publisher=Fly foundry |access-date=13 March 2015 |date=2012 |archive-url=https://web.archive.org/web/20161119104923/http://flyfoundry.com/wes-wadas-signature-flies/featured-fly-juicebug-damsel-nymph/fishing-tips-for-the-juicebug-damsel-nymph/ |archive-date=19 November 2016 |url-status=dead }}</ref>

Damselflies have formed subjects for personal [[jewellery]] such as brooches since at least 1880.<ref>{{cite web|title=Antique "Damselfly" Brooch in Silver-topped Gold with Ruby Eyes|url=http://www.macklowegallery.com/gallery-display-item.asp/antique/Jewelry/Art+Nouveau/Jewelry/antiques/Brooches/item/BO-12758/Brooches/Antique+%93Damselfly%94+Brooch+in+Silver-topped+Gold+with+Ruby+Eyes|publisher=Macklowe Gallery|access-date=13 March 2015 }}{{dead link|date=August 2016|bot=medic}}{{cbignore|bot=medic}}</ref>

''Damselfly'' is a 2005 short film directed by Ben O'Connor.<ref>{{cite web|title=Ben O'Connor|url=http://film.britishcouncil.org/ben-oconnor|publisher=British Council|access-date=13 March 2015}}</ref>

''Damselfly'' is the title of a 2012 novel in the ''Faeble'' series by S. L. Naeole<ref>{{cite book|last1=Naeole|first1=S. L.|title=Damselfly|date=2012|publisher=Crystal Quill}}</ref> and of a 2018 novel by Chandra Prasad.<ref>{{Cite web|title=Damselfly|url=https://rusoffagency.com/fiction/damselfly/|access-date=21 December 2020|website=Marly Rusoff Literary Agency}}</ref>

Modern poems with the damselfly as a subject include a 1994 poem by [[August Kleinzahler]], which contains the lines "And that blue there, cobalt / a moment, then iridescent, / fragile as a lady's pin / hovering above the nasturtium?"<ref>{{cite web |last1=Kleinzahler |first1=August |title=The Damselfly |url=http://www.poetryfoundation.org/poetrymagazine/browse/164/5#!/20604095 |publisher=Poetry Magazine |access-date=13 March 2015 |date=August 1994}}</ref> The poet [[John Engels]] published "Damselfly, Trout, Heron" in his 1983 collection ''Weather-Fear: New and Selected Poems''.<ref>{{cite book |last1=Engels|first1=John |title=Damselfly, Trout, Heron |publisher=University of Georgia Press |url=http://www.poetryfoundation.org/poem/177648 |access-date=13 March 2015 |date=1983}}</ref>

==See also==
* [[List of damselflies of the world]]
* [[List of odonates of Sri Lanka]]
* [[Protozygoptera]], a fossil group that somewhat resembled the damselflies

== Citations ==
{{Reflist|28em}}

== General and cited sources ==
* {{cite book | last=Berger |first=Cynthia |title=Dragonflies |year=2004 |url=https://archive.org/details/dragonflieswildg00cynt | url-access=registration | page=[https://archive.org/details/dragonflieswildg00cynt/page/2 2] |publisher=Stackpole Books |isbn=978-0-8117-2971-0 }}
* {{cite book |last=Dijkstra |first=Klaas-Douwe B. |title=Field Guide to the Dragonflies of Britain and Europe |year=2006 |publisher=British Wildlife Publishing |isbn=978-0-9531399-4-1}}
* {{cite book|last=Paulson|first=Dennis|title=Dragonflies and Damselflies of the West |url=https://books.google.com/books?id=wnX1nJSmFfAC&pg=PA44|year=2009|publisher=Princeton University Press |isbn=978-1-4008-3294-1}}
* {{cite web |last1=Trueman |first1=John W. H. |last2=Rowe |first2=Richard J. |title=Odonata |url=http://tolweb.org/Odonata/8266 |publisher=Tree of Life |date=2009 |access-date=25 February 2015 |archive-date=21 November 2010 |archive-url=https://web.archive.org/web/20101121081529/http://tolweb.org/Odonata/8266 |url-status=dead }}

== External links ==
{{Commons category|Zygoptera}}
{{Wikispecies|Zygoptera}}
{{Wiktionary|damselfly}}
* [http://tolweb.org/Odonata Tree of Life: Odonata]
* [https://entnemdept.ufl.edu/creatures/misc/odonata/odonata.htm Dragonflies and damselflies] on the [[University of Florida|UF]] / [[Institute of Food and Agricultural Sciences|IFAS]] Featured Creatures Web site
* [https://web.archive.org/web/20150227190348/http://www.mndragonfly.org/biology.html Minnesota Dragonfly Society: Biology and Ecology]

{{Odonata|1}}
{{Taxonbar | from=Q230502}}
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[[Category:Damselflies| ]]
[[Category:Articles containing video clips]]
[[Category:Extant Late Jurassic first appearances]]
[[Category:Insects used as insect pest control agents]]
[[Category:Kimmeridgian first appearances]]