Editing Swarm behaviour (section)

===Non-social insects===

Unlike social insects, swarms of non-social insects that have been studied primarily seem to function in contexts such as mating, feeding, predator avoidance, and migration.

====Moths====
Moths may exhibit synchronized mating, during which pheromones released by females initiate searching and swarming behavior in males.<ref>{{cite journal | last1 = Stepien | first1 = T.L. | last2 = Zmurchok | first2 = C. | last3 = Hengenius | first3 = J.B. | last4 = Caja Rivera | first4 = R.M. | last5 = D'Orsogna | first5 = M.R.|author5-link=Maria Rita D'Orsogna | last6 = Lindsay | first6 = A.E. | year = 2000 | title = Moth Mating: Modeling Female Pheromone Calling and Male Navigational Strategies to Optimize Reproductive Success. | journal = Applied Sciences | volume = 10 | issue = 18 | pages = 6543 | doi=10.3390/app10186543| doi-access = free }}</ref> Males sense pheromones with sensitive antennae and may track females as far as several kilometers away.<ref>{{cite journal | last1 = Badeke | first1 = B. | last2 = Haverkamp | first2 = A. | last3 = Sachse | first3 = S.A. | year = 2016 | title = A challenge for a male noctuid moth? Discerning the female sex pheromone against the background of plant volatiles. | journal = Frontiers in Physiology | volume = 7 | pages = 143 | doi=10.3389/fphys.2016.00143| pmid = 27199761 | pmc = 4843018 | doi-access = free }}</ref> Swarm mating involves female choice and male competition. Only one male in the swarm—typically the first—will successfully copulate.<ref>{{cite journal | last1 = Greenfield | first1 = M.D. | year = 1981| title =Moth sex pheromones: an evolutionary perspective. | journal = The Florida Entomologist | volume = 64 | issue = 1| pages = 4–17 | doi=10.2307/3494597| jstor = 3494597 }}</ref> Females maximize [[Fitness (biology)|fitness]] benefits and minimize cost by governing the onset and magnitude of pheromone deployed. Too little pheromone will not attract a mate, too much allows less fit males to sense the signal.<ref>{{cite journal | last1 = Umbers | first1 = K.D.L. | last2 = Symonds | first2 = M.R.E. | last3 = Kokko | first3 = H. | year = 2015 | title = The Mothematics of female pheromone signaling: Strategies for aging virgins. | journal = American Naturalist | volume = 185 | issue = 3 | pages = 417–432 | doi=10.1086/679614| pmid = 25674695 | bibcode = 2015ANat..185..417U | hdl = 1885/13166 | s2cid = 13846468 | url = https://www.zora.uzh.ch/id/eprint/187449/1/50Umbers.pdf | hdl-access = free }}</ref> After copulation, females lay the eggs on a host plant. Quality of host plant may be a factor influencing the location of swarming and egg-laying. In one case, researchers observed pink-striped oakworm moths (''[[Anisota virginiensis]]'') swarming at a [[carrion]] site, where decomposition likely increased soil nutrient levels and host plant quality.<ref>{{cite journal | last1 = Mason | first1 = D.S. | last2 = Baruzzi | first2 = C. | year = 2019 | title = Love in strange places. | journal = Frontiers in Ecology and the Environment | volume = 17 | issue = 3| pages = 184 | doi=10.1002/fee.2027| doi-access = free | bibcode = 2019FrEE...17..184M }}</ref>

====Flies====
Midges, such as ''[[Tokunagayusurika akamusi]],'' form swarms, dancing in the air. Swarming serves multiple purposes, including the facilitation of mating by attracting females to approach the swarm, a phenomenon known as [[lek mating]]. Such cloud-like swarms often form in early evening when the sun is getting low, at the tip of a bush, on a hilltop, over a pool of water, or even sometimes above a person. The forming of such swarms is not out of instinct, but an adaptive behavior – a "consensus" – between the individuals within the swarms. It is also suggested that swarming is a [[ritual]], because there is rarely any male midge by itself and not in a swarm. This could have formed due to the benefit of lowering inbreeding by having males of various genes gathering in one spot.<ref>{{cite web |url=https://nature.mdc.mo.gov/discover-nature/field-guide/midges|title=Midges|website=MDC Discover Nature|language=en|access-date=2019-11-19}}</ref> The genus ''[[Culicoides]]'', also known as biting midges, have displayed swarming behavior which are believed to cause confusion in predators.<ref>{{cite journal |last1=Kirkeby |first1=Carsten |title=Observations of female and mixed sex swarming behaviour in ''Culicoides'' LATREILLE, 1809 (Diptera: Ceratopogonidae) |journal=Polish Journal of Entomology |date=30 June 2018 |volume=87 |issue=2 |pages=191–197 |doi=10.2478/pjen-2018-0014|doi-access=free }}</ref>

====Cockroaches====
[[Cockroach]]es leave chemical trails in their feces as well as emitting airborne [[pheromones]] for mating. Other cockroaches will follow these trails to discover sources of food and water, and also discover where other cockroaches are hiding. Thus, groups of cockroaches can exhibit [[Emergence#Living, biological systems|emergent behaviour]],<ref name="viegas">{{cite web |url=http://animal.discovery.com/news/briefs/20060327/cockroach.html |title=Cockroaches Make Group Decisions |publisher=[[Discovery Channel]] |author=Jennifer Viegas |access-date=10 June 2006 |url-status=dead |archive-url=https://web.archive.org/web/20080704111419/http://animal.discovery.com/news/briefs/20060327/cockroach.html |archive-date=4 July 2008}}</ref> in which group or swarm behaviour emerges from a simple set of individual interactions.

Cockroaches are mainly nocturnal and will run away when exposed to light. A study tested the hypothesis that cockroaches use just two pieces of information to decide where to go under those conditions: how dark it is and how many other cockroaches there are. The study conducted by José Halloy and colleagues at the [[Université Libre de Bruxelles|Free University of Brussels]] and other European institutions created a set of tiny [[robot]]s that appear to the roaches as other roaches and can thus alter the roaches' perception of [[critical mass (sociodynamics)|critical mass]]. The robots were also specially scented so that they would be accepted by the real roaches.<ref>{{cite magazine
|url=http://www.time.com/time/health/article/0,8599,1684427,00.html?imw=Y
|archive-url=https://web.archive.org/web/20071116222235/http://www.time.com/time/health/article/0,8599,1684427,00.html?imw=Y
|url-status=dead
|archive-date=November 16, 2007
|title=Robotic Roaches Do the Trick
|magazine=Time
|first=Michael D.
|last=Lemonick
|date=2007-11-15}}</ref>

====Locusts====
{{See also|Marching locusts}}
[[File:Schwarm Wanderheuschrecke.jpg|thumb|upright|A 19th century depiction of a swarm of [[desert locust]]s]]

[[Locust]]s are the swarming phase of the short-horned [[grasshopper]]s of the family [[Acrididae]]. Some species can breed rapidly under suitable conditions and subsequently become gregarious and migratory. They form bands as [[nymph (biology)|nymphs]] and swarms as adults—both of which can travel great distances, rapidly stripping fields and greatly [[pest (organism)|damaging crops]]. The largest swarms can cover hundreds of square miles and contain billions of locusts. A locust can eat its own weight (about 2&nbsp;grams) in plants every day. That means one million locusts can eat more than one tonne of food each day, and the largest swarms can consume over 100,000 [[tonne]]s each day.<ref>[https://web.archive.org/web/20070625102824/http://animals.nationalgeographic.com/animals/bugs/locust.html Locust ''Locustidae''] ''National Geographic''. Retrieved 12 December 2010.</ref>

Swarming in locusts has been found to be associated with increased levels of [[serotonin]] which causes the locust to change colour, eat much more, become mutually attracted, and breed much more easily. Researchers propose that swarming behaviour is a response to overcrowding and studies have shown that increased tactile stimulation of the hind legs or, in some species, simply encountering other individuals causes an increase in levels of serotonin. The transformation of the locust to the swarming variety can be induced by several contacts per minute over a four-hour period.<ref>{{cite news |url=http://news.bbc.co.uk/2/hi/science/nature/7858996.stm|title=Locust swarms 'high' on serotonin|date=29 January 2009|via=BBC}}</ref><ref>{{cite journal |doi=10.1242/jeb.00648 |vauthors=Rogers SM, Matheson T, Despland E, Dodgson T, Burrows M, Simpson SJ |date= November 2003|title=Mechanosensory-induced behavioural gregarization in the desert locust ''Schistocerca gregaria'' |journal=J. Exp. Biol. |volume=206 |issue=Pt 22 |pages=3991–4002 |pmid=14555739|doi-access=free |bibcode=2003JExpB.206.3991R }}</ref><ref>{{cite journal |doi=10.1126/science.1169280 |last=Stevenson |first=PA |title=The Key to Pandora's Box |journal=Science |volume=323 |issue=5914 |pages=594–5 |year=2009 |pmid=19179520|s2cid=39306643 }}</ref><ref>[https://www.newscientist.com/article/dn16505-blocking-happiness-chemical-may-prevent-locust-plagues.html Blocking 'happiness' chemical may prevent locust plagues], [[New Scientist]], 2009-01-29, accessed 2009-01-31</ref> Notably, an innate predisposition to aggregate has been found in hatchlings of the desert locust, ''[[Schistocerca gregaria]]'', independent of their parental phase.<ref>{{cite journal |doi= 10.1111/j.1744-7917.2012.01518.x |author1=Moshe Guershon |author2=Amir Ayali |date= May 2012 |title=Innate phase behavior in the desert locust, ''Schistocerca gregaria'' |journal= Insect Science |volume=19 |issue=6 |pages=649–656|s2cid=83412818 |doi-access=free |bibcode=2012InsSc..19..649G }}</ref>

An individual locust's response to a loss of alignment in the group appears to increase the randomness of its motion, until an aligned state is again achieved. This noise-induced alignment appears to be an intrinsic characteristic of collective coherent motion.<ref>{{cite journal |doi=10.1073/pnas.0811195106 |last1=Yates |first1=CA |last2=Erban |first2=R |last3=Escudero |first3=C |last4=Couzin |first4=ID |last5= Buhl |first5=J |last6=Kevrekidis |first6=IG |last7=Maini |first7=PK |last8=Sumpter |first8=DJ |title=Inherent noise can facilitate coherence in collective swarm motion |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=106 |issue=14 |pages=5464–9 |year=2009 |pmid=19336580 |pmc=2667078|bibcode= 2009PNAS..106.5464Y|doi-access=free }}</ref>

====Migratory behavior====
[[File:Monarch flock.jpg|thumb|upright|Cluster of [[Monarch butterfly|monarch butterflies]]. Monarch butterflies migrate to [[Santa Cruz, California]], where they [[overwinter]]]]
{{Main|Insect migration}}
{{See also|Lepidoptera migration}}
[[Insect migration]] is the seasonal movement of [[insect]]s, particularly those by species of [[dragonfly|dragonflies]], [[beetle]]s, [[butterfly|butterflies]], and [[moth]]s. The distance can vary from species to species, but in most cases these movements involve large numbers of individuals. In some cases the individuals that migrate in one direction may not return and the next generation may instead migrate in the opposite direction. This is a significant difference from [[bird migration]].

[[Monarch butterfly|Monarch butterflies]] are especially noted for their lengthy annual migration. In North America they make massive southward migrations starting in August until the first frost. A northward migration takes place in the spring. The monarch is the only butterfly that migrates both north and south as the birds do on a regular basis. But no single individual makes the entire round trip. Female monarchs deposit eggs for the next generation during these migrations.<ref>Pyle, Robert Michael, "National Audubon Society Field Guide to North American Butterflies", p712-713, Alfred A. Knopf, New York, {{ISBN|0-394-51914-0}}</ref> The length of these journeys exceeds the normal lifespan of most monarchs, which is less than two months for butterflies born in early summer. The last generation of the summer enters into a non-reproductive phase known as [[diapause]] and may live seven months or more.<ref name="ref1">{{cite web |url=http://www.dbc.uci.edu/~pjbryant/biodiv/lepidopt/danaidae/monarchm.htm |title=Monarch, Danaus plexippus |access-date=2008-08-27 |url-status=dead |archive-url=https://archive.today/20121215095741/http://www.dbc.uci.edu/~pjbryant/biodiv/lepidopt/danaidae/monarchm.htm |archive-date=2012-12-15}}</ref> During diapause, butterflies fly to one of many overwintering sites. The generation that overwinters generally does not reproduce until it leaves the overwintering site sometime in February and March. It is the second, third and fourth generations that return to their northern locations in the United States and Canada in the spring. How the species manages to return to the same overwintering spots over a gap of several generations is still a subject of research; the flight patterns appear to be inherited, based on a combination of the position of the sun in the sky<ref>Gugliotta, Guy (2003): [http://ipm.osu.edu/trans/053_231.htm Butterflies Guided By Body Clocks, Sun Scientists Shine Light on Monarchs' Pilgrimage] {{webarchive|url=https://web.archive.org/web/20060305034410/http://ipm.osu.edu/trans/053_231.htm |date=2006-03-05}}. ''[[Washington Post]]'', May 23, 2003, page A03. Retrieved 2006-JAN-07.</ref> and a time-compensated Sun compass that depends upon a [[circadian clock]] that is based in their antennae.<ref>{{cite journal |vauthors=Merlin C, Gegear RJ, Reppert SM |year= 2009 |title= Antennal Circadian Clocks Coordinate Sun Compass Orientation in Migratory Monarch Butterflies |journal= Science |volume= 325 |issue= 5948 |pages= 1700–1704 |doi= 10.1126/science.1176221 |pmid= 19779201 |pmc= 2754321 |bibcode= 2009Sci...325.1700M}}</ref><ref>{{cite journal |author= Kyriacou CP |year= 2009 |title= Unraveling Traveling |journal= Science |volume= 325 |issue= 5948 |pages= 1629–1630 |doi= 10.1126/science.1178935 |pmid= 19779177|s2cid= 206522416 }}</ref>