It's hard to see in the small colonies because there are so few ants," said Chandra. "But we show statistically that this really is happening and we have instances where it's quite dramatic. So, even in small colonies of clonal raider ants, each ant seems to be following very similar rules for search behavior compared to an army ant, although it might not look like it at first glance. And as you increase colony size, the interactions between these ants lead to greater coordination, you start to see more obvious 'pushing parties' and you start to actually see spontaneous columns of ants leaving the nest."

Scott, Jon (March 2005). "The locust jump: an integrated laboratory investigation" (PDF). Advances in Physiology Education. 29 (1): 21–26. doi: 10.1152/advan.00037.2004. PMID 15718379. S2CID 27101536. Archived from the original (PDF) on 26 February 2019. The relative size and robustness of the locust make it simple to handle and ideal for such investigations. Probably the most common pattern is that collective behavior evolves via natural selection acting on and tweaking the interaction rules that the individual animals follow," said Kronauer. "But our study is a nice example of a different mechanism: scaling effects associated with group size can give you dramatically different outcomes in terms of collective behavior, even though the individual rules don't change much." a b c Kronauer, Daniel J. C. (2009). "Recent advances in army ant biology ( Hymenoptera: Formicidae)". Myrmecological News. 12: 51–65. Simpson, Stephen J.; Sword, Gregory A. (2008). "Locusts". Current Biology. 18 (9): R364–R366. doi: 10.1016/j.cub.2008.02.029. PMID 18460311. Majd, Hooman (23 September 2008). The Ayatollah Begs to Differ: The paradox of modern Iran. Knopf Doubleday Publishing Group. pp.165ff. ISBN 978-0-385-52842-9.El Hage Abd Salam Shabeeny (1820). An account of Timbuctoo and Housa: Territories in the interior of Africa. pp.222–. ISBN 9781613106907. The soldiers of army ants are larger than the workers, and they have much larger mandibles than the worker class of ants, with older soldiers possessing larger heads and stronger mandibles than the younger ones. They protect the colony, and help carry the heaviest loads of prey to the colony bivouac. Chapman JW, Klaassen RHG, Drake VA, Fossette S, Hays GC, Metcalfe JD, et al. Animal orientation strategies for movement in flows. Curr Biol. 2011;21:R861–70. a b c d Krall, S.; Peveling, R.; Diallo, B.D. (1997). New Strategies in Locust Control. Springer Science & Business Media. pp.453–454. ISBN 978-3-7643-5442-8. Swarming behaviour decreased in the 20th century, but despite modern surveillance and control methods, swarms can still form; when suitable weather conditions occur and vigilance lapses, plagues can occur. [5] [6]

A 2003 study of thirty species (by Sean Brady of Cornell University) indicates that army ants of subfamilies Ecitoninae (South America), Dorylinae (Africa) and Aenictinae (Asia) together formed a monophyletic group, based on data from three molecular genes and one mitochondrial gene. Brady concluded that these groups are, therefore, a single lineage that evolved in the mid-Cretaceous period in Gondwana, [n 2] so these subfamilies are now generally united into a single subfamily Dorylinae, though this is still not universally recognized. [38] However, the unification of these lineages means that the only subfamily that is composed solely of legionary species is Leptanillinae, as Dorylinae contains many non-legionary genera. Thomas M.B., Gbongboui C., Lomer C.J. (1996). "Between-season survival of the grasshopper pathogen Metarhizium flavoviride in the Sahel". Biocontrol Science and Technology. 6 (4): 569–573. doi: 10.1080/09583159631208. {{ cite journal}}: CS1 maint: multiple names: authors list ( link)Colonies of real army ants always have only one queen, while some other ant species can have several queens. The queen is dichthadiigyne (a blind ant with large gaster) but may sometimes possess vestigial eyes. [5] The queens of army ants are unique in that they do not have wings, have an enlarged gaster size and an extended cylindrical abdomen. [8] They are significantly larger than worker army ants and possess 10–12 segments on their antennae. [5] Queens will mate with multiple males and because of their enlarged gaster, can produce 3 to 4 million eggs a month, resulting in synchronized brood cycles and colonies composed of millions of individuals all related to a single queen. [5] [10] Behaviour [ edit ] E. vagans with larvae of a raided wasp nest Dorylus sp. in Cameroon, consuming a grasshopper Safari ants ( Dorylus sp.) on a march in Kakamega Forest, Kenya. A column of workers moves under the protection of the soldiers, who link together into a tunnel and display their mandibles to ward off predators Army ant syndrome [ edit ] One of the greatest differences between the solitary and gregarious phases is behavioural. The gregaria nymphs are attracted to each other, this being seen as early as the second instar. They soon form bands of many thousands of individuals. These groups behave like cohesive units and move across the landscape, mostly downhill, but making their way around barriers and merging with other bands. The attraction between the insects involves visual and olfactory cues. [21] The bands seem to navigate using the sun. They pause to feed at intervals before continuing on, and may cover tens of kilometres over a few weeks. [11] Brattström O, Bensch S, Wassenaar LI, Hobson KA, Åkesson S. Understanding the migration ecology of European red admirals Vanessa atalanta using stable isotopes. Ecography. 2008;33:720–9.

Gal agreed, "Of course, it has been long known that changing group size can have a dramatic effect on emergent collective behavior. This has been shown both theoretically and experimentally. We have now shown that this effect can also be harnessed by evolution, and that collective behavior can be adapted over evolutionary timescales without actually modifying the behavior of individuals." Many species of army ants are widely considered to be keystone species [25] due to their important ecological role as arthropod predators [26] and due to their large number of vertebrate and invertebrate associates that rely on army ant colonies for nutrition or protection. [27] [28] [29] During their hunt, many surface-raiding army ants are accompanied by various birds, such as antbirds, thrushes, ovenbirds and wrens, which devour the insects that are flushed out by the ants, a behavior known as kleptoparasitism. [30] [31] A wide variety of arthropods including staphylinid beetles, histerid beetles, spiders, silverfish, isopods, and mites also follow colonies. [32] While some guests follow the colony emigrations on foot, [33] [34] [29] many others are phoretically transported, for example by attaching themseles on army ant workers such as the histerid beetle Nymphister kronaueri. [35] The Neotropical army ant Eciton burchellii has an estimated 350 to 500 animal associates, the most of any one species known to science. [29] Taxonomy [ edit ] Kistner, D. H. (1982). The social insects’ bestiary. In H. R. Hermann (Ed.), Social insects (Vol. III, pp. 1–221). London: Academic. Guo, Xiaojiao; Yu, Qiaoqiao; Chen, Dafeng; Wei, Jianing; Yang, Pengcheng; Yu, Jia; Wang, Xianhui; Kang, Le (2020). "4-Vinylanisole is an aggregation pheromone in locusts". Nature. 584 (7822): 584–588. Bibcode: 2020Natur.584..584G. doi: 10.1038/s41586-020-2610-4. PMID 32788724. S2CID 221106319.

Henningsson SS, Alerstam T. Barriers and distances as determinants for the evolution of bird migration links: the Arctic shorebird system. Proc R Soc B. 2005;272:2251–8. Webster MS, Marra PP, Haig SM, Bensch S, Holmes RT. Links between worlds: unraveling migratory connectivity. Trends Ecol Evol. 2002;17:76–83. During the last two millennia, desert locust plagues have appeared sporadically in Africa, the Middle East, and Europe. Other species of locusts caused havoc in North and South America, Asia, and Australasia; in China, 173 outbreaks over 1924 years. [36] The Bombay locust ( Nomadacris succincta) was a major pest in India and southeastern Asia in the 18th and 19th centuries, but has seldom swarmed since the last plague in 1908. [38] Morgan, James (29 January 2009). "Locust swarms 'high' on serotonin". BBC News. Archived from the original on 10 October 2013 . Retrieved 4 March 2014. Determined movement away from the current home range - In other words, if it looks like a migration, it probably is a migration. Migrating insects move with a mission, making persistent progress away from their existing range and toward a new one.

Cohen EB, Hostetler JA, Hallworth MT, Rushing CS, Sillett TS, Marra PP. Quantifying the strength of migratory connectivity. Methods Ecol Evol. 2018;9:513–24. Composition database for Biodiversity" (Version2, BioFoodComp2ed.). FAO. 10 January 2013 . Retrieved 1 April 2015. These insects, also known as warrior or legionary ants, are present in most tropical and subtropical areas of the planet. They move about in groups of between 10,000 and 200,000 adult workers, which can cover surfaces up to 65 feet wide and 650 feet long.

About

Thomas, M. C. The American grasshopper, Schistocerca americana americana (Drury) (Orthoptera: Acrididae). [ permanent dead link] Entomology Circular No. 342. Florida Department of Agriculture and Consumer Services. May 1991. Most ant species will send individual scouts to find food sources and later recruit others from the colony to help; however, army ants dispatch a cooperative, leaderless group of foragers to detect and overwhelm the prey at once. [3] [5] Army ants do not have a permanent nest but instead form many bivouacs as they travel. The constant traveling is due to the need to hunt large amounts of prey to feed its enormous colony population. [5] Their queens are wingless and have abdomens that expand significantly during egg production. [8] This allows for the production of 3–4 million eggs every month and often results in synchronized brood cycles, thus each colony will be formed of millions of individuals that descend from a single queen. These three traits are found in all army ant species and are the defining traits of army ants. [3] [11] Nomadic and stationary phase [ edit ] Their mass raids are considered the pinnacle of collective foraging behavior in the animal kingdom. The raids are a coordinated hunting swarm of thousands and, in some species, millions of ants. The ants spontaneously stream out of their nest, moving across the forest floor in columns to hunt for food. The raids are one of the most iconic collective behaviors in the animal kingdom. Scientists have studied their ecology and observed their complex behavior extensively. And while we know how these raids happen, we know nothing of how they evolved. Morris GM, Kline C, Morris SM. Status of Danaus plexippus population in Arizona. J Lepid Soc. 2015;69:91–107.