Editing Swarm behaviour (section)

===Social insects===
[[File:Mueckenschwarm 50p 1600kbit.ogv|thumb|left|Swarm of [[nematocera]], flying around a treetop]]

The behaviour of social insects (insects that live in [[colony (biology)|colonies]], such as ants, bees, wasps and termites) has always been a source of fascination for children, naturalists and artists. Individual insects seem to do their own thing without any central control, yet the colony as a whole behaves in a highly coordinated manner.<ref name=SwarmSmarts>Bonabeau E and Theraulaz G (2008) "Swarm Smarts". In ''Your Future with Robots'' Scientific American Special Editions.</ref> Researchers have found that cooperation at the colony level is largely [[self-organization|self-organized]]. The group coordination that emerges is often just a consequence of the way individuals in the colony interact. These interactions can be remarkably simple, such as one ant merely following the trail left by another ant. Yet put together, the cumulative effect of such behaviours can solve highly complex problems, such as locating the shortest route in a network of possible paths to a food source. The organised behaviour that emerges in this way is sometimes called [[swarm intelligence]], a form of [[Emergence#Living, biological systems|biological emergence]].<ref name=SwarmSmarts/>

====Ants====
{{See also|Ant colony|Ant colony optimization algorithm|Ant mill|Ant robotics}}
[[File:Red weaver ants transporting a dead gecko, in Laos (video).webm|thumb|right|A swarm of weaver ants (''[[Oecophylla smaragdina]]'') transporting a dead gecko]]

Individual [[ants]] do not exhibit complex behaviours, yet a colony of ants collectively achieves complex tasks such as constructing nests, taking care of their young, building bridges and [[foraging]] for food. A colony of ants can collectively select (i.e. send most workers towards) the best, or closest, food source from several in the vicinity.<ref>{{cite journal |last1=Czaczkes|first1=T.J.|last2=Grüter|first2=C.|last3=Ratnieks|first3=F. L. W.|title=Trail pheromones: an integrative view of their role in colony organisation|journal=Annual Review of Entomology|date=2015|volume=60|pages=581–599|doi=10.1146/annurev-ento-010814-020627|pmid=25386724|s2cid=37972066|doi-access=free}}</ref> Such collective decisions are achieved using positive feedback mechanisms. Selection of the best food source is achieved by ants following two simple rules. First, ants which find food return to the nest depositing a [[pheromone]] chemical. More pheromone is laid for higher quality food sources.<ref>{{cite journal |last1=Beckers|first1=R.|last2=Deneubourg|first2=J. L.|last3=Goss|first3=S|title=Modulation of trail laying in the ant Lasius niger (Hymenoptera: Formicidae) and its role in the collective selection of a food source|journal=Journal of Insect Behavior|date=1993|volume=6|issue=6|pages=751–759|doi=10.1007/BF01201674|bibcode=1993JIBeh...6..751B |citeseerx=10.1.1.161.9541|s2cid=14670150}}</ref> Thus, if two equidistant food sources of different qualities are found simultaneously, the pheromone trail to the better one will be stronger. Ants in the nest follow another simple rule, to favor stronger trails, on average. More ants then follow the stronger trail, so more ants arrive at the high quality food source, and a positive feedback cycle ensures, resulting in a collective decision for the best food source. If there are two paths from the ant nest to a food source, then the colony usually selects the shorter path. This is because the ants that first return to the nest from the food source are more likely to be those that took the shorter path. More ants then retrace the shorter path, reinforcing the pheromone trail.<ref>{{cite journal |last1=Goss|first1=S.|last2=Aron|first2=S.|last3=Deneubourg|first3=J. L.|last4=Pasteels|first4=J. M.|title=Self-organized shortcuts in the Argentine ant|journal=Naturwissenschaften|date=1989|volume=76|issue=12|pages=579–581|doi=10.1007/BF00462870|bibcode=1989NW.....76..579G|s2cid=18506807|url=https://dipot.ulb.ac.be/dspace/bitstream/2013/19271/1/042GossNaturwissenschaften89.pdf}}</ref>

[[Army ant]]s, unlike most ant species, do not construct permanent nests; an army ant colony moves almost incessantly over the time it exists, remaining in an essentially perpetual state of swarming. Several lineages have independently evolved the same basic behavioural and ecological syndrome, often referred to as "legionary behaviour", and may be an example of [[convergent evolution]].<ref name=brady2003>{{Cite journal |last1= Brady |first1= Seán G. |title = Evolution of the army ant syndrome: The origin and long-term evolutionary stasis of a complex of behavioral and reproductive adaptations |journal= Proceedings of the National Academy of Sciences of the United States of America |volume= 100 |issue = 11 |pages= 6575–9 |date=2003 |pmid= 12750466 |pmc= 164488 |doi= 10.1073/pnas.1137809100|bibcode= 2003PNAS..100.6575B |doi-access= free }}</ref>

The successful techniques used by [[ant colonies]] have been studied in computer science and [[robotics]] to produce [[distributed system|distributed]] and [[fault-tolerant system]]s for solving problems. This area of [[biomimetics]] has led to studies of ant locomotion, search engines that make use of "foraging trails", fault-tolerant storage and [[:Category:Networking algorithms|networking algorithms]].<ref name="SANdisk">{{cite book |vauthors=Dicke E, Byde A, Cliff D, Layzell P |year=2004 |chapter=An ant-inspired technique for storage area network design |title=Proceedings of Biologically Inspired Approaches to Advanced Information Technology: First International Workshop, BioADIT 2004 LNCS 3141 |url=https://archive.org/details/biologicallyinsp2004ijsp |url-access=limited |pages=[https://archive.org/details/biologicallyinsp2004ijsp/page/n378 364]–379 |publisher=Springer |isbn=9783540233398 |editor1=A. J. Ispeert |editor2=M. Murata |editor3=N. Wakamiya}}</ref>

====Honey bees====
[[File:Bee swarm feb08.jpg|thumb|upright|Bees swarming on a tree]]
{{Main|Bees algorithm|Swarming (honey bee)}}

In temperate climates, [[honey bee]]s usually form swarms in late spring. A swarm typically contains about half the workers together with the old queen, while the new queen stays back with the remaining workers in the original hive. When honey bees emerge from a hive to form a swarm, they may gather on a branch of a tree or on a bush only a few meters from the hive. The bees cluster about the queen and send out 20–50 scouts to find suitable new nest locations. The scouts are the most experienced foragers in the cluster. If a scout finds a suitable location, she returns to the cluster and promotes it by dancing a version of the [[waggle dance]]. This dance conveys information about the quality, direction, and distance of the new site. The more excited she is about her findings, the more vigorously she dances. If she can convince others they may take off and check the site she found. If they approve they may promote it as well. In this decision-making process, scouts check several sites, often abandoning their own original site to promote the superior site of another scout. Several different sites may be promoted by different scouts at first. After some hours and sometimes days, a preferred location eventually emerges from this decision-making process. When all scouts agree on the final location, the whole cluster takes off and swarms to it. Sometimes, if no decision is reached, the swarm will separate, some bees going in one direction; others, going in another. This usually results in failure, with both groups dying. A new location is typically a kilometre or more from the original hive, though some species, e.g., ''[[Apis dorsata]]'',<ref>{{cite journal |last1=Oldroyd|first1=BP|date=1998|title=Colony relatedness in aggregations of ''Apis dorsata'' Fabricius (Hymenoptera, Apidae)|journal=Insectes Sociaux|volume=47|pages=94–95|doi=10.1007/s000400050015|s2cid=40346464}}</ref> may establish new colonies within as little as 500 meters from the natal nest. This collective decision-making process is remarkably successful in identifying the most suitable new nest site and keeping the swarm intact. A good hive site has to be large enough to accommodate the swarm (about 15 litres in volume), has to be well-protected from the elements, receive an optimal amount of sunshine, be some height above the ground, have a small entrance and be capable of resisting ant infestation - that is why tree cavities are often selected.<ref>Milius, Susan [http://www.sciencenews.org/view/feature/id/43117/title/Swarm_Savvy Swarm Savvy] {{Webarchive|url=https://web.archive.org/web/20120927005309/http://www.sciencenews.org/view/feature/id/43117/title/Swarm_Savvy |date=27 September 2012 }}, How bees, ants and other animals avoid dumb collective decisions; Science News, May 9th, 2009; Vol.175 #10 (p. 16)</ref><ref>[https://www.sciencedaily.com/releases/2008/10/081003081637.htm Bee Swarms Follow High-speed 'Streaker' Bees To Find A New Nest]; ScienceDaily (Nov. 24, 2008)</ref><ref>{{cite journal |last1= Seeley |first1= Thomas D. |last2= Visscher |first2= P. Kirk |year= 2003 |title= Choosing a home: how the scouts in a honey bee swarm perceive the completion of their group decision making |url= http://bees.ucr.edu/reprints/bes54.pdf |journal= Behavioral Ecology and Sociobiology |volume= 54 |issue= 5 |pages= 511–520 |doi= 10.1007/s00265-003-0664-6 |bibcode= 2003BEcoS..54..511S |s2cid= 16948152 |access-date= 14 December 2010 |archive-date= 31 January 2009 |archive-url= https://web.archive.org/web/20090131024024/http://bees.ucr.edu/reprints/bes54.pdf |url-status= dead }}</ref><ref>{{cite journal |last1= Morse |first1= R.A. |year= 1963 |title= Swarm orientation in honeybees |journal= Science |volume= 141 |issue= 3578 |pages= 357–358 |doi=10.1126/science.141.3578.357 |pmid=17815993 |bibcode= 1963Sci...141..357M|s2cid= 46516976 }}</ref><ref>{{cite journal |last1= Seeley |first1= Thomas |year= 2003 |title= Consensus building during nest-site selection in honey bee swarms: The expiration of dissent |journal= Behavioral Ecology and Sociobiology |volume= 53 |issue= 6 |pages= 417–424 |doi= 10.1007/s00265-003-0598-z|bibcode= 2003BEcoS..53..417S |s2cid= 34798300 }}</ref>