Editing Butterfly (section)

==Biology==

===General description===

{{further|Glossary of entomology terms|Comparison of butterflies and moths}}

Butterfly adults are characterized by their four scale-covered wings, which give the Lepidoptera their name ([[Ancient Greek]] λεπίς lepís, scale + πτερόν pterón, wing). These scales give butterfly wings their colour: they are pigmented with [[melanin]]s that give them blacks and browns, as well as [[uric acid]] derivatives and [[flavones]] that give them yellows, but many of the blues, greens, reds and [[Iridescence|iridescent colours]] are created by [[structural coloration]] produced by the micro-structures of the scales and hairs.<ref name=Formfunction/><ref>{{cite journal |last=Mason |first=C. W. |title=Structural Colors in Insects. II |year=1927 |journal=The Journal of Physical Chemistry |volume=31 |pages=321–354 |issue=3 |doi=10.1021/j150273a001}}</ref><ref>{{cite journal |author1=Vukusic, P. |author2=J. R. Sambles |author3=H. Ghiradella |name-list-style=amp |date=2000 |title=Optical Classification of Microstructure in Butterfly Wing-scales |journal=Photonics Science News |volume=6 |pages=61–66}}</ref><ref>{{cite journal |doi=10.1242/jeb.02051 |date=February 2006 |author1=Prum, R. |author2=Quinn, T. |author3=Torres, R. |title=Anatomically Diverse Butterfly Scales all Produce Structural Colours by Coherent Scattering |volume=209 |issue=Pt 4 |pages=748–65 |issn=0022-0949 |pmid=16449568 |journal=The Journal of Experimental Biology |doi-access=free |bibcode=2006JExpB.209..748P |hdl=1808/1600 |hdl-access=free }}</ref>

As in all insects, the body is divided into three sections: the head, [[Thorax (insect anatomy)|thorax]], and [[Abdomen#Arthropoda|abdomen]]. The thorax is composed of three segments, each with a pair of legs. In most families of butterfly the antennae are clubbed, unlike those of [[moth]]s which may be threadlike or feathery. The long proboscis can be coiled when not in use for sipping nectar from flowers.<ref name=Gullan>{{cite book |author1=Gullan, P. J. |author2=Cranston, P. S. |title=The Insects: An Outline of Entomology |edition=5 |url=https://books.google.com/books?id=lF5hBAAAQBAJ&pg=PT790 |year=2014 |publisher=Wiley |isbn=978-1-118-84616-2 |pages=523–524 |access-date=8 January 2016 |archive-date=10 June 2016 |archive-url=https://web.archive.org/web/20160610140427/https://books.google.com/books?id=lF5hBAAAQBAJ&pg=PT790 |url-status=live }}</ref>

<gallery class=center mode=nolines widths="180px" heights="180px">
File:Inachis io top detail MichaD crop.jpg|A zoomed in view of the wing scales on a ''[[Aglais io]]'', or peacock butterfly.
File:Arctia caja Buchstein02.jpg|Most butterflies fly by day, most moths by night: but ''[[Arctia caja]]'' is day-flying.
File:antennae ctb.png|Butterfly antennal shapes, mainly clubbed, unlike those of moths. Drawn by C. T. Bingham, 1905
</gallery>

Nearly all butterflies are [[Diurnal cycle|diurnal]], have relatively bright colours, and hold their wings vertically above their bodies when at rest, unlike the majority of moths which fly by night, are often [[crypsis|cryptically]] coloured (well camouflaged), and either hold their wings flat (touching the surface on which the moth is standing) or fold them closely over their bodies. Some day-flying moths, such as the [[hummingbird hawk-moth]],<ref>{{cite journal |last1 = Herrera |first1=Carlos M. |title=Activity Pattern and Thermal Biology of a Day-Flying Hawkmoth (''Macroglossum stellatarum'') under Mediterranean summer conditions |journal=Ecological Entomology |volume=17 |pages=52–56 |year=1992 |issue=1 |doi=10.1111/j.1365-2311.1992.tb01038.x |bibcode=1992EcoEn..17...52H |hdl=10261/44693 |s2cid=85320151 |hdl-access=free }}</ref> are exceptions to these rules.<ref name=Gullan/><ref>{{cite web |title=Butterflies and Moths (Order Lepidoptera) |url=http://www.amentsoc.org/insects/fact-files/orders/lepidoptera.html |publisher=Amateur Entomologists' Society |access-date=13 September 2015 |archive-date=28 September 2015 |archive-url=https://web.archive.org/web/20150928023032/http://www.amentsoc.org/insects/fact-files/orders/lepidoptera.html |url-status=live }}</ref>

Butterfly [[larva]]e, [[caterpillar]]s, have a hard ([[Sclerotin|sclerotised]]) head with strong mandibles used for cutting their food, most often leaves. They have cylindrical bodies, with ten segments to the abdomen, generally with short prolegs on segments 3–6 and 10; the three pairs of true legs on the thorax have five segments each.<ref name=Gullan/> Many are well camouflaged; others are aposematic with bright colours and bristly projections containing toxic chemicals obtained from their food plants. The [[pupa]] or chrysalis, unlike that of moths, is not wrapped in a cocoon.<ref name=Gullan/>

{{multiple image
 |header = [[Sexual dimorphism]] in ''[[Anthocharis cardamines]]''
 |total_width = 300

 |image1 = Anthocharis cardamines Weinsberg 20080424.jpg
 |alt1 = A mostly white butterfly with orange-tipped wings
 |caption1 = Male

 |image2 = Anthocharis cardamines female (5709794696).jpg
 |alt2 = A mostly white butterfly with smaller black tips on its wings
 |caption2 = Female
}}

Many butterflies are [[Sexual dimorphism|sexually dimorphic]]. Most butterflies have the [[ZW sex-determination system]] where females are the heterogametic sex (ZW) and males homogametic (ZZ).<ref>{{cite journal |pmid=9292232 |date=August 1997 |last1=Traut |first1=W. |last2=Marec |first2=F. |title=Sex Chromosome Differentiation in Some Species of Lepidoptera (Insecta) |volume=5 |issue=5|pages=283–91 |issn=0967-3849 |doi=10.1023/B:CHRO.0000038758.08263.c3 |journal=Chromosome Research|s2cid=21995492 }}</ref>

===Distribution and migration===

{{hatnote|See also: Lists of butterflies of [[List of butterflies of Australia|Australia]] ([[List of butterflies of Tasmania|Tasmania]], [[List of butterflies of Victoria|Victoria]]), [[List of butterflies of Great Britain|Britain]], [[List of butterflies of India|India]], [[List of butterflies of Menorca|Menorca]], [[List of butterflies of North America|North America]], [[List of butterflies of Taiwan|Taiwan]], and [[List of butterflies of Trinidad and Tobago|Trinidad and Tobago]]}}

{{further|Lepidoptera migration|Insect migration|Animal navigation}}

Butterflies are distributed worldwide except Antarctica, totalling some 18,500 species.<ref name=FAQlepsoc/> Of these, 775 are [[Nearctic realm|Nearctic]]; 7,700 [[Neotropical realm|Neotropical]]; 1,575 [[Palearctic realm|Palearctic]]; 3,650 [[Afrotropical realm|Afrotropical]]; and 4,800 are distributed across the combined [[Indomalayan realm|Oriental]] and [[Australasian realm|Australian]]/[[Oceanian realm|Oceania]] regions.<ref name=FAQlepsoc>{{cite web |last1=Williams |first1=Ernest |last2=Adams |first2=James |last3=Snyder |first3=John |title=Frequently Asked Questions |url=http://www.lepsoc.org/frequently_asked_questions.php |publisher=The Lepidopterists' Society |access-date=9 September 2015 |url-status=dead |archive-url=https://web.archive.org/web/20150513015255/http://www.lepsoc.org/frequently_asked_questions.php |archive-date=13 May 2015 }}</ref> The [[monarch butterfly]] is native to the Americas, but in the nineteenth century or before, spread across the world, and is now found in Australia, New Zealand, other parts of Oceania, and the [[Iberian Peninsula]]. It is not clear how it dispersed; adults may have been blown by the wind or larvae or pupae may have been accidentally transported by humans, but the presence of suitable host plants in their new environment was a necessity for their successful establishment.<ref>{{cite web |title=Global Distribution |url=http://monarchlab.org/biology-and-research/biology-and-natural-history/global-distribution |publisher=Monarch Lab |access-date=9 September 2015 |archive-url=https://web.archive.org/web/20151006015821/http://monarchlab.org/biology-and-research/biology-and-natural-history/global-distribution |archive-date=6 October 2015 |url-status=dead }}</ref>

[[File:MonarchWanderungKlein.gif|thumb|left|[[Monarch (butterfly)|Monarch]] migration route]]
[[File:Monarc Butterfly Reserve4, Michoacan, Mexico.JPG|left|thumb|Overwintering monarchs cluster on [[oyamel]] trees near [[Angangueo]], Mexico.]]
Many butterflies, such as the [[Vanessa cardui|painted lady]], monarch, and several [[Danainae|danaine]] migrate for long distances. These migrations take place over a number of generations and no single individual completes the whole trip. The eastern North American population of monarchs can travel thousands of miles south-west to [[Monarch Butterfly Biosphere Reserve|overwintering sites in Mexico]]. There is a reverse migration in the spring.<ref>{{cite journal |url=http://www.sciencenews.org/view/generic/id/348485/description/Chill_turns_monarchs_north |title=Chill Turns Monarchs North; Cold Weather Flips Butterflies' Migratory Path |journal=Science News |date=23 March 2013 |volume=183 |issue=6 |access-date=5 August 2014 |archive-date=2 October 2013 |archive-url=https://web.archive.org/web/20131002070324/http://www.sciencenews.org/view/generic/id/348485/description/Chill_turns_monarchs_north |url-status=live }}</ref><ref>{{cite book |author=Pyle, Robert Michael |title=National Audubon Society Field Guide to North American Butterflies |pages=[https://archive.org/details/audubonsocietyfi00robe/page/712 712–713] |publisher=Alfred A. Knopf |isbn=978-0-394-51914-2 |year=1981 |url=https://archive.org/details/audubonsocietyfi00robe/page/712 }}</ref> It has recently been shown that the British painted lady undertakes a 9,000-mile round trip in a series of steps by up to six successive generations, from tropical Africa to the Arctic Circle — almost double the length of the famous migrations undertaken by monarch.<ref name=BirdGuides>{{cite web|title=Butterfly Conservation: Secrets of Painted Lady migration unveiled|url=http://www.birdguides.com/webzine/article.asp?a=3493|publisher=BirdGuides Ltd|access-date=22 October 2012|date=22 October 2012|archive-date=31 October 2012|archive-url=https://web.archive.org/web/20121031021232/http://www.birdguides.com/webzine/article.asp?a=3493|url-status=live}}</ref> Spectacular large-scale migrations associated with the [[monsoon]] are seen in peninsular India.<ref>{{cite journal |last1=Williams |first1=C. B. |year=1927 |title=A Study of Butterfly Migration in South India and Ceylon, based largely on records by Messrs. G. Evershed, E. E. Green, J. C. F. Fryer and W. Ormiston |journal=Transactions of the Entomological Society of London |volume=75 |issue=1 |pages=1–33 |doi=10.1111/j.1365-2311.1927.tb00054.x| bibcode=1927EcoEn..75....1W }}</ref> Migrations have been studied in more recent times using wing tags and also using [[Hydrogen isotope biogeochemistry|stable hydrogen isotopes]].<ref>{{cite journal |doi=10.4039/Ent1091583-12 |last1=Urquhart |first1=F. A. |last2=Urquhart |first2=N. R. |year=1977 |title=Overwintering Areas and Migratory Routes of the Monarch butterfly (''Danaus p. plexippus'', Lepidoptera: Danaidae) in North America, with Special Reference to the Western Population |journal=Can. Entomol. |volume=109 |issue=12| pages=1583–1589| s2cid=86198255 }}</ref><ref>{{cite journal |doi=10.1073/pnas.95.26.15436 |last1=Wassenaar |first1=L.I. |last2=Hobson |first2=K.A. |year=1998 |title=Natal Origins of Migratory Monarch Butterflies at Wintering Colonies in Mexico: New Isotopic Evidence |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=95 |issue=26| pages=15436–9 |pmid=9860986 |pmc=28060| bibcode=1998PNAS...9515436W |doi-access=free }}</ref>

Butterflies navigate using a time-compensated sun compass. They can see polarized light and therefore orient even in cloudy conditions. The polarized light near the ultraviolet spectrum appears to be particularly important.<ref>{{cite journal |doi=10.1016/j.cub.2003.12.034 |last1=Reppert |first1=Steven M. |last2=Zhu |first2=Haisun |last3=White |first3=Richard H. |year=2004 |title=Polarized light Helps Monarch Butterflies Navigate |journal=Current Biology |volume=14 |issue=2| pages=155–158 |pmid=14738739| s2cid=18022063 |doi-access=free |bibcode=2004CBio...14..155R }}</ref><ref>{{cite journal |doi=10.1016/j.neuron.2005.03.014 |last1=Sauman |first1=Ivo |last2=Briscoe |first2=Adriana D. |last3=Zhu |first3=Haisun |last4=Shi |first4=Dingding |last5=Froy |first5=Oren |last6=Stalleicken |first6=Julia |last7=Yuan |first7=Quan |last8=Casselman |first8=Amy |last9=Reppert |first9=Steven M. |year=2005 |title=Connecting the Navigational Clock to Sun Compass Input in Monarch Butterfly Brain |journal=Neuron |volume=46 |issue=3| pages=457–467 |pmid=15882645 |s2cid=17755509 |display-authors=etal| doi-access=free }}</ref> Many migratory butterflies live in semi-arid areas where breeding seasons are short.<ref>{{cite journal |doi=10.1111/j.1469-185X.1962.tb01609.x |last1=Southwood |first1=T. R. E. |year=1962 |title=Migration of terrestrial arthropods in relation to habitat |journal=Biol. Rev. |volume=37 |issue=2| pages=171–214| s2cid=84711127 }}</ref> The life histories of their host plants also influence butterfly behaviour.<ref>{{cite journal |doi=10.1007/s10841-005-5660-x |last1=Dennis |first1=R L H |last2=Shreeve |first2=Tim G. |last3=Arnold |first3=Henry R. |last4=Roy |first4=David B. |year=2005 |title=Does Diet Breadth Control Herbivorous Insect Distribution Size? Life History and Resource Outlets for Specialist Butterflies |journal=Journal of Insect Conservation |volume=9 |issue=3| pages=187–200| bibcode=2005JICon...9..187D |s2cid=20605146 }}</ref>

===Life cycle===

<!-- NOTE: two redirects ("Butterfly life cycle" & "Life cycles of butterflies") target this section. If renaming the section, please retarget those -->
[[File:Butterfly life cycle diagram in English.svg|thumb|Life cycle of the monarch butterfly]]

Butterflies in their adult stage can live from a week to nearly a year depending on the species. Many species have long larval life stages while others can remain [[Diapause|dormant]] in their pupal or egg stages and thereby survive winters.<ref>{{cite journal |last1=Powell |first1=J. A. |year=1987 |title=Records of Prolonged Diapause in Lepidoptera |journal=[[The Journal of Research on the Lepidoptera]] |volume=25 |issue=2 |pages=83–109| doi=10.5962/p.266734 |s2cid=248727391 |doi-access=free }}</ref> The [[Oeneis melissa|Melissa Arctic]] (''Oeneis melissa'') overwinters twice as a caterpillar.<ref>{{cite web |url=http://www.butterfliesandmoths.org/species/Oeneis-melissa |title=Melissa Arctic |work=Butterflies and Moths of North America |access-date=15 September 2015 |archive-date=28 October 2015 |archive-url=https://web.archive.org/web/20151028164705/http://www.butterfliesandmoths.org/species/Oeneis-melissa |url-status=live }}</ref> Butterflies may have one or more broods per year. The number of generations per year varies from [[Temperateness|temperate]] to [[Tropics|tropical regions]] with tropical regions showing a trend towards [[voltinism|multivoltinism]].<ref>{{cite book |author=Timothy Duane Schowalter |title=Insect Ecology: An Ecosystem Approach |url=https://books.google.com/books?id=2KzokTLIysQC&pg=PA159 |year=2011 |publisher=Academic Press |isbn=978-0-12-381351-0 |page=159 |access-date=8 January 2016 |archive-date=25 April 2016 |archive-url=https://web.archive.org/web/20160425180814/https://books.google.com/books?id=2KzokTLIysQC&pg=PA159 |url-status=live }}</ref>

[[File:Mating Pair of Spotted Fritillaries on Greater Pignut.JPG|thumb|left|Mating pair of [[Melitaea didyma|spotted fritillaries]] on [[Bunium bulbocastanum|greater pignut]]]]
[[File:Thymelicus sylvestris m1.JPG|thumb|left|The male small skipper (''[[Thymelicus sylvestris]]'') has [[pheromone]]-releasing "sex brands" (dark line) on the upperside of its forewings.]]

[[courtship display|Courtship]] is often aerial and often involves [[pheromone]]s. Butterflies then land on the ground or on a perch to mate.<ref name=Gullan/> Copulation takes place tail-to-tail and may last from minutes to hours. Simple photoreceptor cells located at the genitals are important for this and other adult behaviours.<ref>{{cite journal |last1=Arikawa |first1=Kentaro |title=Hindsight of Butterflies: The Papilio butterfly has light sensitivity in the genitalia, which appears to be crucial for reproductive behavior |journal=BioScience |volume=51|issue=3 |pages=219–225 |doi=10.1641/0006-3568(2001)051[0219:HOB]2.0.CO;2 |year=2001 |doi-access=free }}</ref> The male passes a [[spermatophore]] to the female; to reduce sperm competition, he may cover her with his scent, or in some species such as the Apollos (''[[Parnassius]]'') [[Mating plug|plugs her genital opening]] to prevent her from mating again.<ref>{{cite book |last=Schlaepfer |first=Gloria G. |title=Butterflies |url=https://archive.org/details/butterflies0000schl |url-access=registration |year=2006 |publisher=Marshall Cavendish |isbn=978-0-7614-1745-3 |page=[https://archive.org/details/butterflies0000schl/page/52 52]}}</ref>

The vast majority of butterflies have a four-stage life cycle: [[egg]], [[larva]] (caterpillar), [[pupa]] (chrysalis) and [[imago]] (adult). In the genera ''[[Colias]]'', ''[[Erebia]]'', ''[[Euchloe]]'', and ''Parnassius'', a small number of species are known that reproduce [[Parthenogenesis|semi-parthenogenetically]]; when the female dies, a partially developed larva emerges from her abdomen.<ref name=Capinera640/>

====Eggs====

[[File:2012-06-27 Aporia crataegi eggs Malus domestica.JPG|thumb|Eggs of black-veined white (''[[Aporia crataegi]]'') on [[apple]] leaf]]
[[File:Butterfly laying eggs underneath a leaf.jpg|thumb|A butterfly from the genus ''[[Euploea]]'', laying eggs underneath the leaf]]

Butterfly eggs are protected by a hard-ridged outer layer of shell, called the ''chorion''. This is lined with a thin coating of wax which prevents the egg from drying out before the larva has had time to fully develop. Each egg contains a number of tiny funnel-shaped openings at one end, called ''micropyles''; the purpose of these holes is to allow sperm to enter and fertilize the egg. Butterfly eggs vary greatly in size and shape between species, but are usually upright and finely sculptured. Some species lay eggs singly, others in batches. Many females produce between one hundred and two hundred eggs.<ref name=Capinera640>{{cite book |author=Capinera, John L. |title=Encyclopedia of Entomology |url=https://books.google.com/books?id=i9ITMiiohVQC&pg=PA640 |year=2008 |publisher=Springer Science & Business Media |isbn=978-1-4020-6242-1 |page=640 |access-date=8 January 2016 |archive-date=20 May 2016 |archive-url=https://web.archive.org/web/20160520021643/https://books.google.com/books?id=i9ITMiiohVQC&pg=PA640 |url-status=live }}</ref>

Butterfly eggs are fixed to a leaf with a special glue which hardens rapidly. As it hardens it contracts, deforming the shape of the egg. This glue is easily seen surrounding the base of every egg forming a meniscus. The nature of the glue has been little researched but in the case of ''[[Pieris brassicae]]'', it begins as a pale yellow granular secretion containing acidophilic proteins. This is viscous and darkens when exposed to air, becoming a water-insoluble, rubbery material which soon sets solid.<ref>{{cite journal |author1=Beament, J.W.L. |author2=Lal, R. |year=1957 |title=Penetration Through the Egg-shell of ''Pieris brassicae'' |journal=Bulletin of Entomological Research |volume=48 |issue=1 |pages=109–125 |doi=10.1017/S0007485300054134}}</ref> Butterflies in the genus ''[[Agathymus]]'' do not fix their eggs to a leaf; instead, the newly laid eggs fall to the base of the plant.<ref name=Scott121>{{cite book |author=Scott, James A. |title=The Butterflies of North America: A Natural History and Field Guide |url=https://books.google.com/books?id=Oa5m8gZcGjMC&pg=PA121 |year=1992 |publisher=Stanford University Press |isbn=978-0-8047-2013-7 |page=121 |access-date=8 January 2016 |archive-date=18 May 2016 |archive-url=https://web.archive.org/web/20160518162206/https://books.google.com/books?id=Oa5m8gZcGjMC&pg=PA121 |url-status=live }}</ref>

Eggs are almost invariably laid on plants. Each species of butterfly has its own host plant range and while some species of butterfly are restricted to just one species of plant, others use a range of plant species, often including members of a common family.<ref>{{cite book |author=Capinera, John L. |title=Encyclopedia of Entomology |url=https://books.google.com/books?id=i9ITMiiohVQC&pg=PA676 |year=2008 |publisher=Springer Science & Business Media |isbn=978-1-4020-6242-1 |page=676 |access-date=8 January 2016 |archive-date=2 May 2016 |archive-url=https://web.archive.org/web/20160502065723/https://books.google.com/books?id=i9ITMiiohVQC&pg=PA676 |url-status=live }}</ref> In some species, such as the [[great spangled fritillary]], the eggs are deposited close to but not on the food plant. This most likely happens when the egg overwinters before hatching and where the host plant loses its leaves in winter, as do [[Viola (plant)|violets]] in this example.<ref name=Shepard55>{{cite book |author1=Shepard, Jon |author2=Guppy, Crispin |title=Butterflies of British Columbia: Including Western Alberta, Southern Yukon, the Alaska Panhandle, Washington, Northern Oregon, Northern Idaho, and Northwestern Montana |url=https://books.google.com/books?id=il6rJ7glHNQC&pg=PA55 |year=2011 |publisher=UBC Press |isbn=978-0-7748-4437-6 |page=55 |access-date=8 January 2016 |archive-date=13 May 2016 |archive-url=https://web.archive.org/web/20160513010746/https://books.google.com/books?id=il6rJ7glHNQC&pg=PA55 |url-status=live }}</ref>

The egg stage lasts a few weeks in most butterflies, but eggs laid close to winter, especially in temperate regions, go through a [[diapause]] (resting) stage, and the hatching may take place only in spring.<ref>{{cite web |title=British Butterflies: Education: Butterflies in Winter |url=http://www.britishbutterflies.co.uk/winter.asp |access-date=12 September 2015 |archive-url=https://web.archive.org/web/20170107044348/http://www.britishbutterflies.co.uk/winter.asp |archive-date=7 January 2017 |url-status=dead }}</ref> Some temperate region butterflies, such as the [[Nymphalis antiopa|Camberwell beauty]], lay their eggs in the spring and have them hatch in the summer.<ref>{{cite web |title=Camberwell Beauty |url=http://www.luontoportti.com/suomi/en/perhoset/camberwell-beauty |publisher=NatureGate |access-date=12 September 2015 |archive-url=https://web.archive.org/web/20170421061806/http://www.luontoportti.com/suomi/en/perhoset/camberwell-beauty |archive-date=21 April 2017 |url-status=dead }}</ref>

====Caterpillar larva====

[[File:Papilionidae - Papilio machaon-2.JPG|thumb|[[Aposematism|Aposematic]] caterpillar of ''[[Papilio machaon]]'', in threat pose]]

Butterfly larvae, or caterpillars, consume plant leaves and spend practically all of their time searching for and eating food. Although most caterpillars are herbivorous, a few species are [[Predation|predators]]: ''[[Spalgis epius]]'' eats [[scale insect]]s,<ref>{{cite journal |author1=Venkatesha, M. G. |author2=Shashikumar, L. |author3=Gayathri Devi, S.S. |year=2004 |title=Protective Devices of the Carnivorous Butterfly, ''Spalgis epius'' (Westwood) (Lepidoptera: Lycaenidae) |journal=Current Science |volume=87 |issue=5 |pages=571–572}}</ref> while lycaenids such as ''[[Liphyra brassolis]]'' are [[myrmecophily|myrmecophilous]], eating ant larvae.<ref name="Bingham">{{cite book |last1=Bingham |first1=C.T. |author-link=Charles Thomas Bingham |title=The Fauna of British India, Including Ceylon and Burma |url=https://archive.org/details/butterflies02bingiala |volume=II |edition=1st |publisher= [[Taylor & Francis|Taylor and Francis, Ltd.]] |location=London |year=1907 }}</ref>

[[File:Catapaecilma major by Balakrishnan Valappil (7385361012).jpg|thumb|left|[[Mutualism (biology)|Mutualism]]: ant tending a [[Lycaenidae|lycaenid]] caterpillar, ''[[Catapaecilma major]]'']]

Some larvae, especially those of the [[Lycaenidae]], form [[Mutualism (biology)|mutual associations]] with ants. They communicate with the ants using vibrations that are transmitted through the [[Substrate (biology)|substrate]] as well as using chemical signals.<ref>{{cite journal |last=Devries |first=P. J. |title=The larval Ant-organs of Thisbe irenea (Lepidoptera: Riodinidae) and Their Effects Upon Attending Ants |year=1988 |journal=Zoological Journal of the Linnean Society |volume=94 |issue=4 |doi=10.1111/j.1096-3642.1988.tb01201.x |pages=379–393}}</ref><ref>{{cite journal |last=Devries |first=P. J. |title=Enhancement of Symbioses Between Butterfly Caterpillars and Ants by Vibrational Communication |date=June 1990 |journal=Science |volume=248 |issue=4959 |doi=10.1126/science.248.4959.1104 |pmid=17733373 |pages=1104–1106|bibcode=1990Sci...248.1104D |s2cid=35812411 }}</ref> The ants provide some degree of protection to these larvae and they in turn gather [[Honeydew (secretion)|honeydew secretions]]. [[Large blue]] (''Phengaris arion'') caterpillars trick ''[[Myrmica]]'' ants into taking them back to the [[ant colony]] where they feed on the ant eggs and larvae in a parasitic relationship.<ref name="Corruption">{{cite journal |last1=Thomas |first1=Jeremy |last2=Schönrogge |first2=Karsten |last3=Bonelli |first3=Simona |last4=Barbero |first4=Francesca |last5=Balletto |first5=Emilio |title=Corruption of Ant Acoustical Signals by Mimetic Social Parasites |journal=Communicative and Integrative Biology |year=2010 |volume=3 |issue=2 |pages=169–171 |pmid=20585513 |pmc=2889977 |doi=10.4161/cib.3.2.10603}}</ref>

[[File:Four-horned Sphinx (Elm Sphinx).jpg|thumb|[[Camouflage|Cryptic]] [[countershading|countershaded]] caterpillar of a hawkmoth, ''[[Ceratomia amyntor]]'']]

Caterpillars mature through a series of developmental stages known as [[instar]]s. Near the end of each stage, the larva undergoes a process called [[apolysis]], mediated by the release of a series of [[neurohormone]]s. During this phase, the [[cuticle]], a tough outer layer made of a mixture of [[chitin]] and specialized [[protein]]s, is released from the softer [[Squamous epithelium|epidermis]] beneath, and the epidermis begins to form a new cuticle. At the end of each instar, the larva [[ecdysis|moults]], the old cuticle splits and the new cuticle expands, rapidly hardening and developing pigment.<ref name=Klowden>{{cite book |author=Klowden, Marc J. |title=Physiological Systems in Insects |url=https://books.google.com/books?id=CABp1YL0F8gC&pg=PA114 |year=2013 |publisher=Academic Press |isbn=978-0-12-415970-9 |page=114 |access-date=8 January 2016 |archive-date=1 May 2016 |archive-url=https://web.archive.org/web/20160501221755/https://books.google.com/books?id=CABp1YL0F8gC&pg=PA114 |url-status=live }}</ref> <!--Development of butterfly wing patterns begins by the last larval instar.-->

Caterpillars have short antennae and several [[Simple eye in invertebrates|simple eyes]]. The [[Insect mouthparts|mouthparts]] are adapted for chewing with powerful mandibles and a pair of maxillae, each with a segmented palp. Adjoining these is the labium-hypopharynx which houses a tubular spinneret which is able to extrude silk.<ref name=Formfunction/> Caterpillars such as those in the genus ''[[Calpodes]]'' (family Hesperiidae) have a specialized tracheal system on the 8th segment that function as a primitive lung.<ref name="Locke 1997">{{cite journal |last=Locke |first=Michael |title=Caterpillars have evolved lungs for hemocyte gas exchange |journal=Journal of Insect Physiology |volume=44 |issue=1 |year=1997 |doi=10.1016/s0022-1910(97)00088-7 |pmid=12770439 |pages=1–20 |bibcode=1997JInsP..44....1L |url=https://www.academia.edu/33633960/Caterpillars_have_evolved_lungs_for_hemocyte_gas_exchange<!--full text, unlike DOI--> |access-date=19 June 2018 |archive-date=19 July 2021 |archive-url=https://web.archive.org/web/20210719044641/https://www.academia.edu/33633960/Caterpillars_have_evolved_lungs_for_hemocyte_gas_exchange |url-status=live }}</ref> Butterfly caterpillars have three pairs of true legs on the thoracic segments and up to six pairs of [[proleg]]s arising from the abdominal segments. These prolegs have rings of tiny hooks called crochets that are engaged hydrostatically and help the caterpillar grip the substrate.<ref>{{cite web |url=http://www.naturemuseum.org/online/thebutterflylab/anatomy/larva.html |archive-url=https://web.archive.org/web/20120319072020/http://www.naturemuseum.org/online/thebutterflylab/anatomy/larva.html |archive-date=19 March 2012 |title=Peggy Notebaert Nature Museum |publisher=Chicago Academy of Sciences |work=Larva Legs |access-date=7 June 2012}}</ref> The epidermis bears tufts of [[seta]]e, the position and number of which help in identifying the species. There is also decoration in the form of hairs, wart-like protuberances, horn-like protuberances and spines. Internally, most of the body cavity is taken up by the gut, but there may also be large silk glands, and special glands which secrete distasteful or toxic substances. The developing wings are present in later stage instars and the [[gonad]]s start development in the egg stage.<ref name=Formfunction/>

====Pupa====

[[File:Chrysalis5504.jpg|thumb|upright|[[Chrysalis]] of [[gulf fritillary]]]]

When the larva is fully grown, hormones such as [[prothoracicotropic hormone]] (PTTH) are produced. At this point the larva stops feeding, and begins "wandering" in the quest for a suitable pupation site, often the underside of a leaf or other concealed location. There it spins a button of silk which it uses to fasten its body to the surface and moults for a final time. While some caterpillars spin a [[Pupa#Cocoon|cocoon]] to protect the pupa, most species do not. The naked pupa, often known as a chrysalis, usually hangs head down from the cremaster, a spiny pad at the posterior end, but in some species a silken girdle may be spun to keep the pupa in a head-up position.<ref name=Capinera640/> Most of the tissues and cells of the larva are broken down inside the pupa, as the constituent material is rebuilt into the imago. The structure of the transforming insect is visible from the exterior, with the wings folded flat on the ventral surface and the two halves of the proboscis, with the antennae and the legs between them.<ref name=Formfunction>{{cite encyclopedia |url=https://www.britannica.com/animal/lepidopteran/Form-and-function |title=Lepidopteran: Form and function |author=Culin, Joseph |encyclopedia=Encyclopædia Britannica |access-date=8 September 2015 |archive-date=21 September 2017 |archive-url=https://web.archive.org/web/20170921192451/https://www.britannica.com/animal/lepidopteran/Form-and-function |url-status=live }}</ref>

The pupal transformation into a butterfly through [[metamorphosis]] has held great appeal to mankind. To transform from the miniature wings visible on the outside of the pupa into large structures usable for flight, the pupal wings undergo rapid mitosis and absorb a great deal of nutrients. If one wing is surgically removed early on, the other three will grow to a larger size. In the pupa, the wing forms a structure that becomes compressed from top to bottom and pleated from proximal to distal ends as it grows, so that it can rapidly be unfolded to its full adult size. Several boundaries seen in the adult colour pattern are marked by changes in the expression of particular transcription factors in the early pupa.<ref name="pmid11676917">{{cite journal |author1=Brunetti, Craig R. |author2=Selegue, Jayne E. |author3=Monteiro, Antonia |author4=French, Vernon |author5=Brakefield, Paul M. |author6=Carroll, Sean B. |year=2001 |title=The Generation and Diversification of Butterfly Eyespot Color Patterns |journal=Current Biology |volume=11 |issue=20 |pages=1578–1585 |doi=10.1016/S0960-9822(01)00502-4 |pmid=11676917|s2cid=14290399 |doi-access=free |bibcode=2001CBio...11.1578B }}</ref>

====Adult====

[[File:ParthenosSylviaButterfly.jpg|thumb|An adult ''[[Parthenos sylvia]]'' butterfly]]

The reproductive stage of the insect is the winged adult or [[imago]]. The surface of both butterflies and moths is covered by scales, each of which is an outgrowth from a single [[Epidermis|epidermal]] cell. The head is small and dominated by the two large [[Eye#Compound eyes|compound eyes]]. These are capable of distinguishing flower shapes or motion but cannot view distant objects clearly. Colour perception is good, especially in some species in the blue/violet range. The [[Antenna (biology)|antennae]] are composed of many segments and have clubbed tips (unlike moths that have tapering or feathery antennae). The sensory receptors are concentrated in the tips and can detect odours. Taste receptors are located on the palps and on the feet. The mouthparts are adapted to sucking and the [[mandible]]s are usually reduced in size or absent. The first maxillae are elongated into a tubular [[proboscis]] which is curled up at rest and expanded when needed to feed. The first and second maxillae bear palps which function as sensory organs. Some species have a reduced proboscis or maxillary palps and do not feed as adults.<ref name=Formfunction/>

Many ''[[Heliconius]]'' butterflies also use their proboscis to feed on pollen;<ref>{{Cite journal|pmid = 25958827|year = 2015|last1 = Harpel|first1 = D.|title = Pollen feeding proteomics: Salivary proteins of the passion flower butterfly, Heliconius melpomene|journal = Insect Biochemistry and Molecular Biology|volume = 63|pages = 7–13|last2 = Cullen|first2 = D. A.|last3 = Ott|first3 = S. R.|last4 = Jiggins|first4 = C. D.|last5 = Walters|first5 = J. R.|doi = 10.1016/j.ibmb.2015.04.004| bibcode=2015IBMB...63....7H |s2cid=39086740 |url = https://lirias.kuleuven.be/handle/123456789/509592|access-date = 8 November 2018|archive-date = 19 July 2021|archive-url = https://web.archive.org/web/20210719044718/https://limo.libis.be/primo-explore/fulldisplay?docid=LIRIAS528183&context=L&vid=Lirias&search_scope=Lirias&tab=default_tab&lang=en_US&fromSitemap=1|url-status = live|hdl = 2381/37010|hdl-access = free}}</ref> in these species only 20% of the amino acids used in reproduction come from larval feeding, which allow them to develop more quickly as caterpillars, and gives them a longer lifespan of several months as adults.<ref>{{cite web |url=https://sta.uwi.edu/fst/lifesciences/sites/default/files/lifesciences/documents/ogatt/Heliconius_ethilla%20-%20Ethilia%20Longwing%20Butterfly.pdf |title=The Online Guide to the Animals of Trinidad and Tobago {{!}} ''Heliconius ethilla'' (Ethilia Longwing Butterfly) |publisher=UWI St. Augustine |access-date=28 May 2018 |archive-date=28 May 2018 |archive-url=https://web.archive.org/web/20180528215909/https://sta.uwi.edu/fst/lifesciences/sites/default/files/lifesciences/documents/ogatt/Heliconius_ethilla%20-%20Ethilia%20Longwing%20Butterfly.pdf |url-status=live }}</ref>

The thorax of the butterfly is devoted to locomotion. Each of the three thoracic segments has two legs (among [[Nymphalidae|nymphalids]], the first pair is reduced and the insects walk on four legs). The second and third segments of the thorax bear the wings. The leading edges of the forewings have thick veins to strengthen them, and the hindwings are smaller and more rounded and have fewer stiffening veins. The forewings and hindwings are not hooked together ([[Wing coupling (Lepidoptera anatomy)|as they are in moths]]) but are coordinated by the friction of their overlapping parts. The front two segments have a pair of [[Spiracle (arthropods)|spiracle]]s which are used in respiration.<ref name=Formfunction/>

The abdomen consists of ten segments and contains the gut and genital organs. The front eight segments have spiracles and the terminal segment is modified for reproduction. The male has a pair of clasping organs attached to a ring structure, and during copulation, a tubular structure is extruded and inserted into the female's vagina. A [[spermatophore]] is deposited in the female, following which the sperm make their way to a seminal receptacle where they are stored for later use. In both sexes, the genitalia are adorned with various spines, teeth, scales and bristles, which act to prevent the butterfly from mating with an insect of another species.<ref name=Formfunction/> After it emerges from its pupal stage, a butterfly cannot fly until the wings are unfolded. A newly emerged butterfly needs to spend some time inflating its wings with [[hemolymph]] and letting them dry, during which time it is extremely vulnerable to predators.<ref>{{cite book |last=Woodbury |first=Elton N. |title=Butterflies of Delmarva |url=https://books.google.com/books?id=cDNHAAAAYAAJ |year=1994 |publisher=Delaware Nature Society; Tidewater Publishers |isbn=978-0-87033-453-5 |page=22 |access-date=8 January 2016 |archive-date=9 May 2016 |archive-url=https://web.archive.org/web/20160509035428/https://books.google.com/books?id=cDNHAAAAYAAJ |url-status=live }}</ref>

==== Pattern formation ====

The colourful patterns on many butterfly wings tell potential predators that they are toxic. Hence, the genetic basis of wing [[pattern formation]] can illuminate both the [[evolution]] of butterflies as well as their [[developmental biology]]. The colour of butterfly wings is derived from tiny structures called scales, each of which have their own [[pigment]]s. In ''[[Heliconius]]'' butterflies, there are three types of scales: yellow/white, black, and red/orange/brown scales. Some mechanism of wing pattern formation are now being solved using genetic techniques. For instance, a [[gene]] called ''cortex'' determines the colour of scales: deleting ''cortex'' turned black and red scales yellow. Mutations, e.g. [[Transposable element|transposon insertions]] of the [[non-coding DNA]] around the ''cortex'' gene can turn a black-winged butterfly into a butterfly with a yellow wing band.<ref>{{Cite journal |last1=Livraghi |first1=Luca |last2=Hanly |first2=Joseph J |last3=Van Bellghem |first3=Steven M |last4=Montejo-Kovacevich |first4=Gabriela |last5=van der Heijden |first5=Eva SM |last6=Loh |first6=Ling Sheng |last7=Ren |first7=Anna |last8=Warren |first8=Ian A |last9=Lewis |first9=James J |last10=Concha |first10=Carolina |last11=Hebberecht |first11=Laura |date=2021-07-19 |title=Cortex cis-regulatory switches establish scale colour identity and pattern diversity in Heliconius |journal=eLife |volume=10 |pages=e68549 |doi=10.7554/eLife.68549 |pmid=34280087 |issn=2050-084X |pmc=8289415 |doi-access=free }}</ref>

===Mating===

When the butterfly ''Bicyclus anynana'' is subjected to repeated inbreeding in the laboratory, there is a dramatic decrease in egg hatching.<ref name="Saccheri1996">Saccheri IJ, Brakefield PM, Nichols RA. "Severe Inbreeding Depression and Rapid Fitness Rebound in the Butterfly ''Bicyclus anynana'' (Satyridae)". ''Evolution''. 1996 Oct; 50 (5): 2000-2013. doi: 10.1111/j.1558-5646.1996.tb03587.x. PMID 28565613</ref> This severe [[inbreeding depression]] is considered to be likely due to a relatively high [[mutation rate]] to recessive [[allele]]s with substantial damaging effects and infrequent episodes of [[inbreeding]] in nature that might otherwise purge such mutations.<ref name = Saccheri1996/> Although ''B. anynana'' experiences inbreeding depression when forcibly inbred in the laboratory it recovers within a few generation when allowed to breed freely.<ref name="Robertson2020">Robertson DN, Sullivan TJ, Westerman EL. Lack of sibling avoidance during mate selection in the butterfly ''Bicyclus anynana''. ''Behavioural Processes''. 2020 Apr; 173: 104062. doi: 10.1016/j.beproc.2020.104062. Epub 2020 Jan 22. PMID 31981681</ref> During mate selection, adult females do not innately avoid or learn to avoid siblings, implying that such detection may not be critical to reproductive fitness.<ref name = Robertson2020/> Inbreeding may persist in ''B anynana'' because the probability of encountering close relatives is rare in nature; that is, movement ecology may mask the deleterious effect of inbreeding resulting in relaxation of selection for active inbreeding avoidance behaviors.

===Behaviour===

[[File:Australian painted lady feeding.jpg|thumb|left|An [[Australian painted lady]] feeding on a flowering shrub]]

Butterflies feed primarily on [[nectar]] from flowers. Some also derive nourishment from [[pollen]],<ref>{{cite journal |last=Gilbert |first=L. E. |year=1972 |title=Pollen Feeding and Reproductive Biology of ''Heliconius'' Butterflies |journal=Proceedings of the National Academy of Sciences |volume=69 |issue=6 |pages=1402–1407 |doi=10.1073/pnas.69.6.1403|pmid=16591992 |pmc=426712 |bibcode=1972PNAS...69.1403G |doi-access=free }}</ref> tree sap, rotting fruit, dung, decaying flesh, and dissolved minerals in wet sand or dirt. Butterflies are important as pollinators for some species of plants. In general, they do not carry as much pollen load as [[bee]]s, but they are capable of moving pollen over greater distances.<ref>{{cite journal|last=Herrera |first=C. M. |year=1987 |title=Components of Pollinator 'Quality': Comparative Analysis of a Diverse Insect Assemblage |journal=Oikos |volume=50 |number=1 |pages=79–90 |url=http://ebd06.ebd.csic.es/pdfs/Herrera.1987.Oikos.pdf |doi=10.2307/3565403 |jstor=3565403 |url-status=dead |archive-url=https://web.archive.org/web/20090225100931/http://ebd06.ebd.csic.es/pdfs/Herrera.1987.Oikos.pdf |archive-date=25 February 2009 }}</ref> [[Flower constancy]] has been observed for at least one species of butterfly.<ref name="Goulson1997">{{cite journal |doi=10.1006/anbe.1996.0390 |last1=Goulson |first1=D. |last2=Ollerton |first2=J. |last3=Sluman |first3=C. |s2cid=620334 |year=1997 |title=Foraging strategies in the small skipper butterfly, ''Thymelicus flavus'': when to switch? |journal=Animal Behaviour |volume=53 |issue=5 |pages=1009–1016 |author1-link=Dave Goulson |url=http://pdfs.semanticscholar.org/1fee/1912f23d50ad0e01e571490db4b60154a0cb.pdf |access-date=24 December 2020 |archive-date=2 March 2021 |archive-url=https://web.archive.org/web/20210302121954/https://pdfs.semanticscholar.org/1fee/1912f23d50ad0e01e571490db4b60154a0cb.pdf |url-status=live }}</ref>

Adult butterflies consume only liquids, ingested through the proboscis. They sip water from damp patches for hydration and feed on nectar from flowers, from which they obtain sugars for energy, and [[sodium]] and other minerals vital for reproduction. Several species of butterflies need more sodium than that provided by nectar and are attracted by sodium in salt; they sometimes land on people, attracted by the salt in human sweat. Some butterflies also visit dung and scavenge rotting fruit or carcasses to obtain minerals and nutrients. In many species, this [[mud-puddling]] behaviour is restricted to the males, and studies have suggested that the nutrients collected may be provided as a [[nuptial gift]], along with the spermatophore, during mating.<ref>{{cite journal |doi=10.1111/j.1095-8312.2005.00539.x |last1=Molleman |first1=Freerk |last2=Grunsven |first2=Roy H. A. |last3=Liefting |first3=Maartje |last4=Zwaan |year=2005 |first4=Bas J. |last5=Brakefield |first5=Paul M. |title=Is Male Puddling Behaviour of Tropical Butterflies Targeted at Sodium for Nuptial Gifts or Activity? |journal=Biological Journal of the Linnean Society |volume=86 |issue=3 |pages=345–361| doi-access= }}</ref>

In [[Hill-topping (biology)|hilltopping]], males of some species seek hilltops and ridge tops, which they patrol in search for females. Since it usually occurs in species with low population density, it is assumed these landscape points are used as meeting places to find mates.<ref>{{cite book |last1=Gochfeld |first1=Michael |last2=Burger |first2=Joanna |title=Butterflies of New Jersey: A Guide to Their Status, Distribution, Conservation, and Appreciation |url=https://books.google.com/books?id=8SzNCNPkgQcC&pg=PA55 |year=1997 |publisher=Rutgers University Press |isbn=978-0-8135-2355-2 |page=55 |access-date=15 May 2018 |archive-date=27 July 2020 |archive-url=https://web.archive.org/web/20200727142317/https://books.google.com/books?id=8SzNCNPkgQcC&pg=PA55 |url-status=live }}</ref>

Butterflies use their antennae to sense the air for wind and scents. The antennae come in various shapes and colours; the hesperiids have a pointed angle or hook to the antennae, while most other families show knobbed antennae. The antennae are richly covered with sensory organs known as [[sensillum|sensillae]]. A butterfly's sense of taste is coordinated by chemoreceptors on the [[Arthropod leg#Insects|tarsi]], or feet, which work only on contact, and are used to determine whether an egg-laying insect's offspring will be able to feed on a leaf before eggs are laid on it.<ref>{{cite web |url=http://www.sandiegozoo.org/animalbytes/t-butterfly.html |title=Article on San Diego Zoo website |publisher=Sandiegozoo.org |access-date=30 March 2009 |archive-date=4 March 2009 |archive-url=https://web.archive.org/web/20090304014910/http://www.sandiegozoo.org/animalbytes/t-butterfly.html |url-status=live }}</ref> Many butterflies use chemical signals, [[pheromone]]s; some have specialized scent scales ([[androconia]]) or other structures ([[coremata]] or "hair pencils" in the Danaidae).<ref>{{cite journal |last1=Birch |first1=M. C. |last2=Poppy |first2=G. M. |title=Scents and Eversible Scent Structures of Male Moths |journal=Annual Review of Entomology |date=1990 |volume=35 |pages=25–58 |url=http://ento.psu.edu/publications/512BirchEtAl1990.pdf |doi=10.1146/annurev.ento.35.1.25 |access-date=12 September 2015 |archive-date=6 October 2015 |archive-url=https://web.archive.org/web/20151006020930/http://ento.psu.edu/publications/512BirchEtAl1990.pdf |url-status=live }}</ref> Vision is well developed in butterflies and most species are sensitive to the ultraviolet spectrum. Many species show sexual dimorphism in the patterns of UV reflective patches.<ref>{{cite journal |last1=Obara |first1=Y. |last2=Hidaki |first2=T. |year=1968 |title=Recognition of the Female by the Male, on the Basis of Ultra-Violet Reflection, in the White Cabbage Butterfly, ''Pieris rapae crucivora'' Boisduval| journal=Proceedings of the Japan Academy| volume=44 |issue=8| pages=829–832| doi=10.2183/pjab1945.44.829 |doi-access=free }}</ref> Colour vision may be widespread but has been demonstrated in only a few species.<ref>{{cite journal |last1=Hirota |first1=Tadao |last2=Yoshiomi |first2=Yoshiomi| year=2004| title=Color Discrimination on Orientation of Female ''Eurema hecabe'' (Lepidoptera: Pieridae) |journal=Applied Entomology and Zoology |volume=39 |issue=2| pages=229–233 |doi=10.1303/aez.2004.229| doi-access=free |bibcode=2004AppEZ..39..229H }}</ref><ref>{{cite journal |last1=Kinoshita |first1=Michiyo |last2=Shimada |first2=Naoko |last3=Arikawa |first3=Kentaro |year=1999 |title=Color Vision of the Foraging Swallowtail Butterfly ''Papilio xuthus'' |journal=The Journal of Experimental Biology |volume=202 |issue=2 |pages=95–102 |doi=10.1242/jeb.202.2.95 |pmid=9851899 |bibcode=1999JExpB.202...95K |url=https://ir.soken.ac.jp/?action=repository_action_common_download&item_id=3270&item_no=1&attribute_id=22&file_no=1 |access-date=10 August 2021 |archive-date=2 November 2018 |archive-url=https://web.archive.org/web/20181102203420/https://ir.soken.ac.jp/?action=repository_action_common_download&item_id=3270&item_no=1&attribute_id=22&file_no=1 |url-status=live }}</ref> Some butterflies have organs of hearing and some species make [[Stridulation|stridulatory]] and clicking sounds.<ref>{{cite journal |last1=Swihart |first1=S. L |year=1967 |title=Hearing in Butterflies |journal=Journal of Insect Physiology |volume=13 |issue=3| pages=469–472 |doi=10.1016/0022-1910(67)90085-6}}</ref>

[[File:Butterfly midflight.jpg|thumb|left|''Heteronympha merope'' taking off]]

Many species of butterfly maintain territories and actively chase other species or individuals that may stray into them. Some species will bask or perch on chosen perches. The flight styles of butterflies are often characteristic and some species have courtship flight displays. Butterflies can only fly when their temperature is above {{convert|27|°C}}; when it is cool, they can position themselves to expose the underside of the wings to the sunlight to heat themselves up. If their body temperature reaches {{convert|40|°C}}, they can orientate themselves with the folded wings edgewise to the sun.<ref>{{Cite magazine |title=Butterflies Make Best Use of the Sunshine |url=https://books.google.com/books?id=PfHEmTgmHacC&pg=PA13 |archive-date=21 May 2016 |archive-url=https://web.archive.org/web/20160521070952/https://books.google.com/books?id=PfHEmTgmHacC&pg=PA13 |url-status=live |magazine=[[New Scientist]] |volume=120 |issue=1643 |date=17 December 1988 |page=13 |issn=0262-4079 |access-date=8 January 2016 }}</ref> Basking is an activity which is more common in the cooler hours of the morning. Some species have evolved dark wingbases to help in gathering more heat and this is especially evident in alpine forms.<ref>{{cite journal |last1=Ellers |first1=J. |last2=Boggs |first2=Carol L. |year=2002 |title=The Evolution of Wing Color in ''Colias'' Butterflies: Heritability, Sex Linkage, and population divergence |url=http://www.stanford.edu/group/CCB/Pubs/Boggs_pdfs/2002_Ellers_Boggs_Coliaswingcolor.pdf |journal=Evolution |volume=56 |issue=4 |pages=836–840 |pmid=12038541 |doi=10.1554/0014-3820(2002)056[0836:teowci]2.0.co;2 |s2cid=8732686 |access-date=7 November 2006 |archive-date=7 January 2007 |archive-url=https://web.archive.org/web/20070107023814/http://www.stanford.edu/group/CCB/Pubs/Boggs_pdfs/2002_Ellers_Boggs_Coliaswingcolor.pdf |url-status=live }}</ref>

As in many other insects, the [[lift (force)|lift]] generated by butterflies is more than can be accounted for by steady-state, non-transitory [[aerodynamics]]. Studies using ''[[Vanessa atalanta]]'' in a [[wind tunnel]] show that they use a wide variety of aerodynamic mechanisms to generate force. These include [[wake capture]], [[vortices]] at the wing edge, rotational mechanisms and the [[Torkel Weis-Fogh|Weis-Fogh]] '[[clap-and-fling]]' mechanism. Butterflies are able to change from one mode to another rapidly.<ref>{{cite journal |last1=Srygley |first1=R. B. |last2=Thomas |first2=A. L. R. |year=2002 |title=Aerodynamics of Insect Flight: Flow Visualisations with Free Flying Butterflies Reveal a Variety of Unconventional Lift-Generating Mechanisms |journal=Nature |volume=420 |issue=6916| pages=660–664 |pmid=12478291 |doi=10.1038/nature01223| bibcode=2002Natur.420..660S |s2cid=11435467 }}</ref>

===Ecology===

====Parasitoids, predators, and pathogens====

[[File:Braconid parasitoid wasp Apanteles sp eggs & Lime Butterfly (Papilio demoleus) cat W IMG 2862.jpg|thumb|[[Braconid]] [[parasitoid]]al wasp (''[[Apanteles]]'' species) cocoons attached to lime butterfly (''[[Papilio demoleus]]'') caterpillar]]

Butterflies are threatened in their early stages by [[parasitoid]]s and in all stages by predators, diseases and environmental factors. [[Braconidae|Braconid]] and other parasitic wasps lay their eggs in lepidopteran eggs or larvae and the wasps' parasitoid larvae devour their hosts, usually pupating inside or outside the desiccated husk. Most wasps are very specific about their host species and some have been used as biological controls of pest butterflies like the [[Pieris brassicae|large white butterfly]].<ref name=Feltwell401>{{cite book |author=Feltwell, J. |title=Large White Butterfly: The Biology, Biochemistry and Physiology of ''Pieris brassicae'' (Linnaeus) |url=https://books.google.com/books?id=8XnrCAAAQBAJ&pg=PA401 |year=2012 |publisher=Springer |isbn=978-94-009-8638-1 |pages=401– |access-date=8 January 2016 |archive-date=10 May 2016 |archive-url=https://web.archive.org/web/20160510071358/https://books.google.com/books?id=8XnrCAAAQBAJ&pg=PA401 |url-status=live }}</ref> When the [[Pieris rapae|small cabbage white]] was accidentally introduced to New Zealand, it had no natural enemies. In order to control it, some pupae that had been parasitised by a chalcid wasp were imported, and natural control was thus regained.<ref>{{cite book |author1=Burton, Maurice |author2=Burton, Robert |title=International Wildlife Encyclopedia: Brown bear - Cheetah |url=https://books.google.com/books?id=WLIOwLemzyQC&pg=PA416 |year=2002 |publisher=Marshall Cavendish |isbn=978-0-7614-7269-8 |page=416 |access-date=8 January 2016 |archive-date=9 May 2016 |archive-url=https://web.archive.org/web/20160509074556/https://books.google.com/books?id=WLIOwLemzyQC&pg=PA416 |url-status=live }}</ref> Some flies lay their eggs on the outside of caterpillars and the newly hatched fly larvae bore their way through the skin and feed in a similar way to the parasitoid wasp larvae.<ref name=Allen>{{cite book |author=Allen, Thomas J. |title=A Field Guide to Caterpillars |url=https://books.google.com/books?id=SS6s7tck0fIC&pg=PA15 |year=2005 |publisher=Oxford University Press |isbn=978-0-19-803413-1 |page=15 |access-date=8 January 2016 |archive-date=27 April 2016 |archive-url=https://web.archive.org/web/20160427045848/https://books.google.com/books?id=SS6s7tck0fIC&pg=PA15 |url-status=live }}</ref> Predators of butterflies include ants, spiders, wasps, and birds.<ref>{{cite web |title=Parasites and Natural Enemies |url=http://monarchlab.org/biology-and-research/biology-and-natural-history/parasites-natural-enemies |publisher=University of Minnesota |access-date=16 October 2015 |archive-date=7 October 2015 |archive-url=https://web.archive.org/web/20151007132714/http://monarchlab.org/biology-and-research/biology-and-natural-history/parasites-natural-enemies/ |url-status=live }}</ref>

Caterpillars are also affected by a range of bacterial, viral and fungal diseases, and only a small percentage of the butterfly eggs laid ever reach adulthood.<ref name=Allen/> The bacterium ''[[Bacillus thuringiensis]]'' has been used in sprays to reduce damage to crops by the caterpillars of the large white butterfly, and the [[entomopathogenic fungus]] ''[[Beauveria bassiana]]'' has proved effective for the same purpose.<ref name=Feltwell429>{{cite book |author=Feltwell, J. |title=Large White Butterfly: The Biology, Biochemistry and Physiology of ''Pieris Brassicae'' (Linnaeus) |url=https://books.google.com/books?id=8XnrCAAAQBAJ&pg=PA429 |year=2012 |publisher=Springer |isbn=978-94-009-8638-1 |page=429 |access-date=8 January 2016 |archive-date=5 May 2016 |archive-url=https://web.archive.org/web/20160505022425/https://books.google.com/books?id=8XnrCAAAQBAJ&pg=PA429 |url-status=live }}</ref>

====Endangered species====

[[Queen Alexandra's birdwing]], found in [[Papua New Guinea]], is the largest butterfly in the world. The species is [[List of endangered insects#Other Lepidoptera species|endangered]], and is one of only three insects (the other two being butterflies as well) to be listed on [[CITES#Appendix I|Appendix I]] of [[CITES]], making international trade illegal.<ref name="CITES appendices">[http://www.cites.org/eng/app/appendices.php CITES appendices I, II and III] {{Webarchive|url=https://web.archive.org/web/20171205014647/http://www.cites.org/eng/app/appendices.php |date=5 December 2017 }}, official website</ref>

====Defences====

{{further|Defense in insects|Anti-predator adaptation|Mimicry|Seasonal polyphenism}}

Butterflies protect themselves from predators by a variety of means.

Chemical defences are widespread and are mostly based on chemicals of plant origin. In many cases the plants themselves evolved these toxic substances as [[plant defense against herbivory|protection]] against herbivores. Butterflies have evolved mechanisms to sequester these plant toxins and use them instead in their own defence.<ref>{{cite journal |doi=10.1146/annurev.ento.47.091201.145121 |last1=Nishida |first1=Ritsuo |year=2002 |title=Sequestration of Defensive Substances from Plants by Lepidoptera |journal=Annual Review of Entomology |volume=47 |pages=57–92 |pmid=11729069}}</ref> These defence mechanisms are effective only if they are well advertised; this has led to the evolution of bright colours in unpalatable butterflies ([[aposematism]]). This signal is commonly [[mimicry|mimicked]] by other butterflies, usually only females. A [[Batesian mimicry|Batesian mimic]] imitates another species to enjoy the protection of that species' aposematism.<ref name=Edmunds/> The [[Papilio polytes|common Mormon]] of India has female morphs which imitate the unpalatable red-bodied swallowtails, the [[Pachliopta aristolochiae|common rose]] and the [[Pachliopta hector|crimson rose]].<ref>{{cite web |last1=Halloran |first1=Kathryn |last2=Wason |first2=Elizabeth |title=''Papilio polytes'' |url=http://animaldiversity.org/accounts/Papilio_polytes/ |website=Animal Diversity Web |publisher=University of Michigan Museum of Zoology |access-date=12 September 2015 |date=2013 |archive-date=7 October 2015 |archive-url=https://web.archive.org/web/20151007182812/http://animaldiversity.org/accounts/Papilio_polytes/ |url-status=live }}</ref> [[Müllerian mimicry]] occurs when aposematic species evolve to resemble each other, presumably to reduce predator sampling rates; ''[[Heliconius]]'' butterflies from the Americas are a good example.<ref name=Edmunds>{{cite book |author=Edmunds, M. |year=1974 |title=Defence in Animals |url=https://archive.org/details/defenceinanimals0000edmu |url-access=registration |publisher=Longman |pages=[https://archive.org/details/defenceinanimals0000edmu/page/74 74]–78, 100–113}}</ref>

[[Camouflage]] is found in many butterflies. Some like the oakleaf butterfly and [[Doleschallia bisaltide|autumn leaf]] are remarkable imitations of leaves.<ref>{{cite journal |doi=10.1086/283868 |last1=Robbins |first1=Robert K. |s2cid=34146954 |year=1981 |title=The "False Head" Hypothesis: Predation and Wing Pattern Variation of Lycaenid Butterflies |journal=American Naturalist |volume=118 |issue=5| pages=770–775| bibcode=1981ANat..118..770R }}</ref> As caterpillars, many defend themselves by freezing and appearing like sticks or branches.<ref>{{cite book| author=Forbes, Peter |date=2009 |title=Dazzled and Deceived: Mimicry and Camouflage |publisher=Yale University Press |isbn=978-0-300-17896-8|title-link=Dazzled and Deceived: Mimicry and Camouflage }}</ref> Others have [[deimatic]] behaviours, such as rearing up and waving their front ends which are marked with eyespots as if they were snakes.<ref name=Springer>{{cite web |url=http://www.springerreference.com/docs/html/chapterdbid/86053.html |title=Deimatic Behavior |publisher=Springer |year=2012 |access-date=31 December 2012 |author=Edmunds, Malcolm |archive-date=28 July 2013 |archive-url=https://web.archive.org/web/20130728153247/http://www.springerreference.com/docs/html/chapterdbid/86053.html |url-status=live }}</ref> Some papilionid caterpillars such as the giant swallowtail (''[[Papilio cresphontes]]'') resemble bird droppings so as to be passed over by predators.<ref>{{cite web |title=Featured Creatures: Giant Swallowtail |url=http://entnemdept.ifas.ufl.edu/creatures/citrus/giantswallowtail.htm |publisher=University of Florida |access-date=12 September 2015 |archive-date=11 June 2019 |archive-url=https://web.archive.org/web/20190611201118/https://entnemdept.ifas.ufl.edu/creatures/citrus/giantswallowtail.htm |url-status=live }}</ref> Some caterpillars have hairs and bristly structures that provide protection while others are gregarious and form dense aggregations.<ref name=Edmunds/> Some species are [[myrmecophile]]s, forming [[Symbiosis|mutualistic associations]] with [[ant]]s and gaining their protection.<ref>{{cite journal|author1=Fiedler, K. |author2=Holldobler, B. |author3=Seufert, P. |title=Butterflies and Ants: The Communicative Domain |journal=Cellular and Molecular Life Sciences |volume=52 |date=1996 |pages=14–24 |doi=10.1007/bf01922410|s2cid=33081655 }}</ref> Behavioural defences include perching and angling the wings to reduce shadow and avoid being conspicuous. Some female [[Nymphalid]] butterflies guard their eggs from parasitoidal [[wasp]]s.<ref>{{cite journal |last1 = Nafus |first1 = D. M. |last2 = Schreiner |first2 = I. H. |year = 1988 |title = Parental Care in a Tropical Nymphalid Butterfly ''Hypolimas anomala'' |journal = Animal Behaviour |volume = 36 |issue = 5| pages = 1425–1443 |doi=10.1016/s0003-3472(88)80213-6| s2cid = 53183529 }}</ref>

The Lycaenidae have a false head consisting of eyespots and small tails (false antennae) to deflect attack from the more vital head region. These may also cause ambush predators such as spiders to approach from the wrong end, enabling the butterflies to detect attacks promptly.<ref>{{cite journal |author=Cooper, William E. Jr. |year=1998 |title=Conditions Favoring Anticipatory and Reactive Displays Deflecting Predatory Attack |journal=Behavioral Ecology |volume=9 |issue=6 |pages=598–604 |doi=10.1093/beheco/9.6.598|citeseerx=10.1.1.928.6688 }}</ref><ref>{{cite journal |doi=10.1017/S1464793105006810 |last1=Stevens |first1=M. |s2cid=24868603 |year=2005 |title=The Role of Eyespots as Anti-Predator Mechanisms, Principally Demonstrated in the Lepidoptera |journal=Biological Reviews |volume=80 |issue=4| pages=573–588 |pmid=16221330}}</ref> Many butterflies have [[Eyespot (mimicry)|eyespots]] on the wings; these too may deflect attacks, or may serve to attract mates.<ref name="pmid11676917" /><ref name ="Eyespot">{{cite journal |author=Brakefield, PM |year=1996 |title=Development, Plasticity and Evolution of Butterfly Eyespot Patterns |journal=Nature |issue=6606| pages=236–242 |volume=384 |doi=10.1038/384236a0 |pmid=12809139| last2=Gates |first2=Julie |last3=Keys |first3=Dave |last4=Kesbeke |first4=Fanja |last5=Wijngaarden |first5=Pieter J. |last6=Montelro |first6=Antónia |last7=French |first7=Vernon |last8=Carroll |first8=Sean B. |display-authors=etal| bibcode=1996Natur.384..236B |s2cid=3341270 }}</ref>

Auditory defences can also be used, which in the case of the [[grizzled skipper]] refers to vibrations generated by the butterfly upon expanding its wings in an attempt to communicate with ant predators.<ref>{{Cite journal|last=Elfferich|first=Nico W.|date=1998|title=Is the larval and imaginal signalling of Lycaenidae and other Lepidoptera related to communication with ants|url=http://natuurtijdschriften.nl/search?identifier=538588|journal=Deinsea|volume=4|issue=1|access-date=6 November 2017|archive-date=27 September 2017|archive-url=https://web.archive.org/web/20170927000340/http://natuurtijdschriften.nl/search?identifier=538588|url-status=live}}</ref>

Many tropical butterflies have [[seasonal polyphenism|seasonal forms]] for dry and wet seasons.<ref>{{cite journal |pmid=18811432 |date=December 1998 |author1=Brakefield, P. M. |author2=Kesbeke, F. |author3=Koch, P. B. |title=The Regulation of Phenotypic Plasticity of Eyespots in the Butterfly ''Bicyclus anynana'' |volume=152 |issue=6 |pages=853–60 |issn=0003-0147 |doi=10.1086/286213 |journal=The American Naturalist|bibcode=1998ANat..152..853B |s2cid=22355327 }}</ref><ref>{{cite journal |doi=10.1006/mpev.2000.0872 |last1=Monteiro |first1=A. |last2=Pierce |first2=N. E. |s2cid=20314608 |year=2001 |title=Phylogeny of Bicyclus (Lepidoptera: Nymphalidae) Inferred from COI, COII, and EF-1 Alpha Gene Sequences |journal=Molecular Phylogenetics and Evolution |volume=18 |issue=2 |pages=264–281 |pmid=11161761| bibcode=2001MolPE..18..264M |url=http://pdfs.semanticscholar.org/ab63/4db58a38ab7e6d3f77f71e96f16157b0b37b.pdf |archive-url=https://web.archive.org/web/20190303094544/http://pdfs.semanticscholar.org/ab63/4db58a38ab7e6d3f77f71e96f16157b0b37b.pdf |url-status=dead |archive-date=2019-03-03 }}</ref> These are switched by the hormone [[ecdysone]].<ref>{{cite journal |pmid=12492404 |date=Jan 2003 |author=Nijhout, Hf |s2cid=6027259 |title=Development and Evolution of Adaptive Polyphenisms |volume=5 |issue=1 |pages=9–18 |issn=1520-541X |journal=Evolution & Development |doi=10.1046/j.1525-142X.2003.03003.x}}</ref> The dry-season forms are usually more cryptic, perhaps offering better camouflage when vegetation is scarce. Dark colours in wet-season forms may help to absorb solar radiation.<ref>{{cite journal |last1=Brakefield |first1=Paul M. |last2=Larsen |first2=Torben B. |title=The Evolutionary Significance of Dry and Wet Season Forms in some Tropical Butterflies |year=1984 |journal=Biological Journal of the Linnean Society |volume=22 |doi=10.1111/j.1095-8312.1984.tb00795.x |pages=1–12 |hdl=1887/11011 |url=https://openaccess.leidenuniv.nl/bitstream/handle/1887/11011/029_009.pdf?sequence=1 |hdl-access=free |access-date=23 September 2019 |archive-date=27 July 2020 |archive-url=https://web.archive.org/web/20200727075120/https://openaccess.leidenuniv.nl/bitstream/handle/1887/11011/029_009.pdf?sequence=1 |url-status=live }}</ref><ref>{{cite journal |doi=10.1098/rspb.2003.2571 |last1=Lyytinen |first1=A. |last2=Brakefield |first2=P. M. |last3=Lindström |first3=L. |last4=Mappes |first4=J. |year=2004 |title=Does Predation Maintain Eyespot Plasticity in ''Bicyclus anynana'' |journal=Proceedings of the Royal Society B |volume=271 |issue=1536| pages=279–283| pmc=1691594 |pmid=15058439}}</ref><ref name ="Eyespot"/>

Butterflies without defences such as toxins or mimicry protect themselves through a flight that is more bumpy and unpredictable than in other species. It is assumed this behavior makes it more difficult for predators to catch them, and is caused by the [[turbulence]] created by the small whirlpools formed by the wings during flight.<ref>{{Cite web|url=https://www.insidescience.org/news/mathematical-butterfly-simulations-provide-new-insights-flight|title=The Mathematical Butterfly: Simulations Provide New Insights On Flight|website=Inside Science|date=19 April 2013 |access-date=15 May 2018|archive-date=16 May 2018|archive-url=https://web.archive.org/web/20180516014712/https://www.insidescience.org/news/mathematical-butterfly-simulations-provide-new-insights-flight|url-status=live}}</ref>

<gallery class=center mode=nolines widths="180px" heights="180px">
File:Heliconius mimicry.png|''[[Heliconius]]'' warns off predators with [[Müllerian mimicry]].<ref>{{cite journal |doi=10.1371/journal.pbio.0040341 |date=October 2006 |last=Meyer |first=A. |title=Repeating Patterns of Mimicry |volume=4 |issue=10 |pages=e341 |issn=1544-9173 |pmid=17048984 |pmc=1617347 |journal=PLOS Biology |doi-access=free }}</ref>
File:Papilio cresphontes larva defensive.JPG|[[Giant swallowtail]] caterpillar everting its [[osmeterium]] in defence; it is also [[mimesis (biology)|mimetic]], resembling a bird dropping.
File:Bird-damaged Speckled Wood Pararge aegeria.JPG|Eyespots of [[Speckled wood (butterfly)|speckled wood]] (''Pararge aegeria'') distract predators from attacking the head. This insect can still fly with a damaged left hindwing.
</gallery>