Dorylus

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Dorylus
Dorylus emeryi

Dorylus emeryi

Systematics
Order : Hymenoptera (Hymenoptera)
Subordination : Waist Wasps (Apocrita)
Superfamily : Vespoidea
Family : Ants (Formicidae)
Subfamily : Dorylinae
Genre : Dorylus
Scientific name of the  subfamily
Dorylinae
Leach , 1815
Scientific name of the  genus
Dorylus
Fabricius , 1793

Dorylus is a genus of ants . It is the only genus of the subfamily Dorylinae . It belongs to the wandering ants (Dorylomorpha). In its ecology and way of life, it corresponds tothe species of the subfamily Ecitoninae in Americain the Old World . The Dorylus species are known as army or driver ants (Driver Ants in English, Siafu in Swahili ). They were named driver ants after the species of the subgenus Anomma , which seem to drive their fleeing prey on a broad front.

The genus Dorylus includes with Dorylus wilverthi the largest ants at all, the queens reach a body length of 52 millimeters, as well as the largest known insect states with more than 20 million workers per colony.

Hunting parade of driver ants
Running track of driver ants
Safari ants in Kenya
Dorylus helvolus
Dorylus nigricans

description

The genus Dorylus is characterized by a single, nodular petiolus . A pinched postpetiolus is not developed, so they can be easily distinguished from the related genus Aenictus . The formation of the clypeus on the head is also typical . This is extremely shortened in the males, completely absent in queens and workers. As a result, the deflection of the antennas is moved directly to the front edge of the head capsule. The front keels are very short, and the antennae are usually noticeably shortened. Depending on the type, they consist of nine to twelve members.

Workers

The workers have a cylindrical body with a very large head. Both ocelles and complex eyes are completely absent. The animals are probably not completely blind, but can at least differentiate between light and dark with a sense of skin light. From the mouthparts, the mandibles are elongated and more or less sickle-shaped with parallel inner and outer edges, i. H. The basal margin and anterior margin (chewing bar) merge into one another without a step. They are the main weapons for predatory food acquisition and are easily able to penetrate human skin. The mandibles have a sharp, sickle-shaped tooth at the tip and usually another, noticeably enlarged tooth in the middle (subapical), but this is variable depending on the type and size. There are also several small teeth. The palps of the maxilla and labium are only two-parted (exception: Dorylus orientalis with one -parted maxillary palps ) and remarkably short compared to most other ants. The labrum is not, as is the case with almost all ants, cut in the middle by a recess, but evenly rounded. The seam between the pronotum and the mesopleur is clearly visible on the trunk , but is immobilized by a narrow band-shaped zone. On the posterior corners of the propodeum (the first abdominal segment fused with the thorax) there are no lobes (often imprecisely called metapleural lobes). On the abdomen, the belly plate (sternite) of the first gastric segment is noticeably shortened. The pygidium (tergite of the seventh abdominal segment, forms the rear end of the free abdomen) is two-pointed due to a deep recess. There is a poison sting, but it is shortened, has no function and is hidden in the abdomen.

The elongated cylindrical body shape, the missing eyes, the shortened antennae and palps can be explained as adaptations to a primarily underground way of life. It is assumed that the real driver ants in the sub-genus Anomma that hunt above ground also descend from ancestors living underground.

The extreme size polymorphism of the workers is very striking in all species of the genus. The largest forms have more than a hundred times the body mass of the smallest. The largest forms were often referred to as "soldiers" in the past, and workers are often divided into three sizes. In contrast to the South American Eciton species, however, all size classes merge seamlessly into one another, there are no sharply divided lower castes.

Queens

As with all driver ants, the shape of the queens is characteristically modified, this special characteristic expression is often referred to as "Dichthadiigyn". The queens, like the workers, are completely eyeless and resemble them in general body shape. In particular, they never have wings or even recognizable rudiments of them. Since the colony of the driver ants is founded by splitting the mother colony, the usual wedding flight of ants is not necessary. Queens can therefore only be found in the midst of protective workers, never individually. The abdomen is cylindrical and strongly elongated, in particular the third abdominal segment (the first segment of the gaster) reaches an unusual length, with Dorylus , unlike other driver ants, the seventh segment is also elongated and clearly bilobed. In egg-laying queens, the abdomen is more or less distended (“ physogastric ”) in order to maximize the number of eggs laid. The head is broadened and rounded, the mandibles are linear or sickle-shaped ("falciform") due to the missing subapical tooth. In contrast to the workers, the queens have a flap-shaped enlargement on each side of the petiolus, on the belly side, whereby the petiolus can reach the width of the trunk when supervised.

male

The males of Dorylus have a completely different appearance compared to the other castes. They have very large, hemispherical protruding complex eyes and also three point eyes (ocelles). They are fully winged and capable of flying. The pronotum is triangularly narrowed when viewed from the side. The abdomen, however, is cylindrical and very noticeably elongated without being narrowed towards the rear. Due to its body shape, which is rather untypical for an ant, the founder of modern taxonomy, Carl von Linné, described the first male available to him as a wasp species and named it Vespa helvola (today: Dorylus helvolus ). Other typical characteristics of the male are: The first three antennae segments are strikingly smooth and shiny, the labial palps are one-segmented, the stigma on the mesothorax is noticeably shifted dorsally compared to its normal position. In the wing veins the weakly developed wing mark (pterostigma) is noticeable, in addition, a cross vein is missing in the fore wing, whereby only a submarginal cell is formed. The shape of the male copulation apparatus also has a number of peculiarities.

The males of the Dorylinae fly en masse at certain times and are attracted in large numbers by light sources. As a result, there are a great many isolated records of finds of males. All systematists therefore suspect that in an unknown number of cases the males were scientifically described a second time independently of the queens and workers. H. one of the species names is synonymous . This has recently been proven for a pair of "species" (" Dorylus gerstaeckeri " is actually the male of Dorylus gribodoi ). The actual number of species of the Dorylinae is very uncertain due to presumably still unrecognized "species" pairs.

In Africa, the males of Dorylus are said to be considered a delicacy and eaten by many peoples. Your name was translated by Europeans as "sausage flies" ("sausage flies").

Larvae

Little is known about the larvae of Dorylus . Some species were described by Wheeler. In terms of their body shape, they correspond to the ant larvae of the "mymecoid" larvae type. H. they are relatively elongated with the body curved towards the abdomen, the abdomen is widest towards the rear end and abruptly narrowed at the rear. Remarkable are leg rudiments that are designed as pillow-shaped, warty structures. The surface of the body is covered with microscopic spindles (spinulae) and only very sparsely hairy. At the head capsule, the labrum and clypeus merge into one another without a clearly recognizable seam; this structure is protruding forward.

Way of life

Most of the Dorylus species, including all Asian (and also the only European) representatives, live and hunt underground (hypogean). The spectacular forays of the actual driver ants are limited to a few species of the subgenus Anomma , all of which live in tropical Africa. While the species that hunt above ground were already noticed by the explorers of the 19th century, much less is known about those that hunt underground. However, this way of life is considered to be the original, from which the above-ground hunting method developed secondarily.

All species, both above ground and underground, show the typical behavior of wandering ants. They always and only hunt in groups made up of numerous workers. There are no scouts who swarm out individually and then recruit nestmates. Instead, the workers break out of the nest every evening in a massive marching column that includes hundreds of thousands to millions of animals. The animals in front run a bit ahead, but then fall back, so that new animals are constantly forming the front. After a certain time, the march column splits into columns running in parallel, which gradually fan out to form a wide front that is one or two meters deep when hunting above-ground species. All marching columns are permanently connected to the nest by animals running back. The animals in front hunt their prey, which at least in the aboveground hunting species includes almost everything, from small mites and springtails to snakes and lizards. Much larger prey animals are also overwhelmed by the synchronous attack of numerous workers; only very few species are safe thanks to special protective mechanisms. The prey animals are then either cut up on the spot or transported to the nest as a whole. The prey is not pulled backwards, as with other ants, but carried lengthways under the body. If a prey object is too big, teams of several workers carry it; this happens more often with Dorylus than with Eciton , which has more very large workers. Towards morning the column returned to the nest, and the following day it set out again in a different direction.

All species hunt on or in the ground, hunting in the field layer or in the crown area of ​​forests does not take place.

If other animal species notice approaching driver ants, this usually leads to immediate flight. In the description of the American zoologist Thomas Staughton Savage , who was the first to describe the animals in detail: "It is literally true that they are driving around anything that is capable of moving. Their arrival in a settlement is recognized by their simultaneous flight of all rats, mice, lizards, cockroaches, etc. living here. And even humans, the self-proclaimed "lord of creation", have to admit defeat to the numerically superior enemy, if the ants come in through one door, they quickly flee through the other. " Due to their highly developed jaw-forceps, driver ants can also inflict very painful bites on humans. In some cases, allergic reactions or shortness of breath may occur. Since a raid by driver ants only covers about 20 meters an hour, the danger for humans is extremely low.

In contrast to the Eciton species, whose brood and queen reside in an aboveground bivouac nest formed from the bodies of workers themselves, all Dorylus species live in underground nests. In the nests, however, there can be bivouac-like gatherings of workers. In the aboveground species Dorylus molestus , the nests are very conspicuous crater-like depressions of about three meters in diameter, the excavated soil was estimated at about 35 kilograms. In the underground hunting Dorylus laevigatus , the nests consist of one or more neighboring burrows up to about 30 centimeters in diameter about 20 centimeters below the surface, with no trace of the nest being visible on the surface. As is typical and characteristic of all wandering ants, all Dorylus species periodically relocate their nest and move into a new nest. In Dorylus molestus the removals were performed according to 3-111 days, mean 17 days. The new nest location was on average about 100 meters from the old one. The nesting sites are usually roughly in a straight line. When moving, only a part of the population moves forward and prepares the new location. Whenever possible, the queen changes her nest in a corridor covered by earth, if one cannot be dug, it is densely covered by workers. The main reason for the move is the exhaustion of the food supply at the old location due to the hunting expeditions, which soon leave no more prey due to the special hunting technique. The complicated rhythms between reproductive and hunting phases described for Eciton species do not exist in Dorylus .

Races of Dorylus , regardless of their number, always have only one queen. New colonies arise from the mother colony by sprouting. At certain intervals, sex animals are created and raised in addition to workers. One or more young queens then leave the mother colony with part of the colony and continue to live independently. Then, in a way that is unknown in detail, excess queens are eliminated. The young queens are fertilized by flown males from other colonies in order to avoid inbreeding. The males fly into the swarm for this. This may give the workers an opportunity to select suitable applicants. Each queen is fertilized by numerous males, but only immediately after splitting. No further fertilization takes place later. Since the workers can have many fathers, they are on average half-sisters. If a queen dies, the affected people perish as a rule. There is neither the formation of replacement sex animals, nor do workers begin to lay eggs (from which males would always hatch because they are not fertilized). Occasionally, however, it happens that a people without a queen merges with another, neighboring people.

If two peoples meet on their hunting expeditions, they usually change their direction of march to avoid each other. There is no significant intraspecific aggression.

The creation of new colonies by sprouting has a number of effects. As a result, it is not possible for the animals to effectively spread over a distance or to cross large areas that are unsuitable for habitat. Probably for this reason, the genus Dorylus is usually absent on islands of all sizes and locations, including the large island of Madagascar. In addition, when their habitat is fragmented, e.g. B. by felling forests, often limited to these habitat islands. They can very quickly become extinct on small islands. Due to their high ecological impact, this has a major impact on the entire community.

Systematics

Sister group of the Dorylinae is probably the enigmatic genus Aenictogiton from South Africa, which is placed in its own subfamily Aenictogitoninae. From Aenictogiton only males have been found to date, workers and queens are unknown. Next is the ancient genus Aenictus , for which a separate subfamily Aenictinae was also established. These together are sister group of the New World Ecitoninae. Thus, all "real" driver ants form a clade, which has been named as Dorylomorpha (in the past, however, all of these subfamilies were usually united in a broader subfamily Dorylinae). This phylogeny appears to be well founded in terms of both morphological and molecular features. Wandering ants in the ecological sense, d. H. There are also species without a permanent nesting site that hunt in groups from other kin groups. In the past, the prevailing view within the Dorylomorpha was that the way of life as a wandering ants developed convergently in the individual subfamilies . Now one assumes a unique, common origin at the base of the trunk line.

In 2000, a Chinese researcher established a second genus of Dorylinae for a newly discovered species, which he named " Yunodorylus sexspinosus ". The species was later placed in the genus Cerapachys (subfamily Cerapachyinae ).

The genus Dorylus is divided into six sub-genera according to morphological characteristics

In a molecular study based on homologous DNA sequences, the outline was confirmed in the main. However, the subgenus Dorylus s turned out to be. st. and Anomma as paraphyletic against each other , they should therefore be united in one group. Monophyletic, on the other hand, was a group that included all Anomma species hunting above ground .

distribution

The main distribution area of ​​the driver ants is in East and Central Africa. Only four species live in Asia. One of them, the widespread Dorylus fulvus , which also lives in the arid regions of North Africa and Arabia, occurs in southeastern Europe (Balkan Peninsula).

Ecological importance

Driver ants are key ecological species in numerous habitats in tropical Africa with a strong influence on the entire community. In terms of area, their biomass can match that of vertebrate predators in the habitats they prefer. The above-ground species apparently influence their habitat more than those that hunt underground. Although some of these specialize in earthworms as their preferred prey, their presence does not permanently lower their biomass. However, the species that hunt underground exert a stronger influence on termite nests. While some subterranean species specialize in this prey, they only exceptionally belong to the prey spectrum of the Epigaean species.

Ant birds

The ant-following bird species should also be mentioned as an example of the influence that the Dorylus species exert on the community. Quite a number of birds have specialized in prey on the frightened insects fleeing from the ants. These types are e.g. Partly completely dependent on the ants. They can be seen as food parasites (kleptoparasites) of the ants, which reduce their hunting success.

In a study in tropical Africa, the authors name 17 bird species for their study areas, which they classify as specialized ant followers: Halcyon badia ( chestnut list ), Ceyx lecontei ( brown-headed pygmy fish ), Phyllastrephus icterinus ( Zeisigbülbül ), Bleda syndactyla , Bleda notata , Criniger chloronotus ( Strichelbrustbülbül ) Criniger calurus ( Swainson-Bülbül ) Stiphrornis erythrothorax ( Waldrötel ) Alethe diademata ( Diademalethe ) Alethe popliocephala ( Braunbrust-Alethe ) Neocossyphus rufus ( Red-Fuchs throttle ) Neocossyphus poensis ( White-Fuchs throttle ) Stizorhina fraseri ( short run throttle ) illadopsis rufipennis ( Gray-illadopsis ) illadopsis fulvescens ( Braunbauch-illadopsis ) illadopsis cleaveri ( eyebrow illadopsis ) Dicrurus atripennis ( Glanzdrongo ). In regions where the ants are disappearing, e.g. B. due to forest clearing, these species cannot survive either.

Folk medicinal use

In earlier times, before modern surgical techniques were available almost worldwide, driver ants, like other ants with particularly wide mandibles, were used to close wounds and to ligate blood vessels. Until the 19th century, ants were held on the edges of the wound and, after their jaws had snapped shut to close the wound, they were severed behind the head. Several ants were used side by side for a longer wound. This technique is said to have been known and described in the ancient civilizations.

literature

Individual evidence

  1. ↑ Jane Goodall: 50 Years at Gombe. Abrams Books, New York, 2013. ISBN 978-1-61312-607-3 . Cape. "Tool Making". (German: My life for animals and nature: 50 years in Gombe. Bassermann Verlag, 2010)
  2. ^ S. Bruce Archibald, Kirk R. Johnson, Rolf W. Mathewes and David R. Greenwood (2011): Intercontinental dispersal of giant thermophilic ants across the Arctic during early Eocene hyperthermals. Proceedings of the Royal Society Series B: 278, 3679-3686, doi: 10.1098 / rspb.2011.0729 , p. 3682
  3. ^ Graeme P. Boswell, Nigel R. Franks, Nicholas F. Britton Arms races and the evolution of big erce societies. Proceedings of the Royal Society Series B 268: 1723-1730, doi: 10.1098 / rspb.2001.1671
  4. ↑ Caspar Schöning, William H. Gotwald, Daniel JC Kronauer, Lars Vilhelmsen: Taxonomy of the African army ant Dorylus gribodoi Emery, 1892 (Hymenoptera, Formicidae) - new insights from DNA sequence data and morphology. In: Zootaxa 1749, 2008, pp. 39-52.
  5. ↑ George Wheeler, Jeanette Wheeler: The larvae of the arma ants (Hymenoptera: Formicidae). A revision. In: Journal of the Kansas Entomological Society 57, No. 2, 1984, pp. 263-275.
  6. ^ Bert Hölldobler, Edward O. Wilson: The Ants. Belknap Press, 1990. ISBN 978-0-674-04075-5 . Chapter 16: The army ants. P. 573 ff.
  7. ↑ NR Franks, AB Sendova-Franks, J. Simmons, M. Mogie: evolution Convergent, super efficient teams and tempo in Old and New World army ants. In: Proceedings of the Royal Society London Series B 266, 1999, pp. 1697-1701.
  8. ↑ Thomas S. Savage: The Driver Ants of Western Africa; On the Identity of Anomma with Dorylus, Suggested by Specimens Which Dr. Savage Found Together, and Transmitted to Illustrate HisPaper on the Driver Ants. In: Proceedings of the Academy of Natural Sciences of Philadelphia , Volume 4 1849, pp. 195-204. Quote on p. 199, download .
  9. ↑ Matebele Ants ( Memento of the original from May 13, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / scienceray.com
  10. ^ H. Youth (2007): Birds in swarm's way. Smithsonian Zoogoer Magazine 36 July / August 2007. ( Archive, article offline ( Memento of the original from August 28, 2011 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. ) @1@ 2Template: Webachiv / IABot / nationalzoo.si.edu
  11. ↑ Caspar Schöning: Evolutionary and behavioral ecology of Dorylus army ants. Chapter 3: Temporal and spatial patterns in the migrating behavior of the army ant Dorylus (Anomma) molestus in the montane forests of Mt Kenya. Diss., FU Berlin 2004.
  12. ↑ Stefanie M. Berghoff: Sociobiology of the hypogeic army ant Dorylus (Dichthadia) laevigatus Fr. Smith. Diss., University of Würzburg 2002.
  13. ↑ DJC Kronauer, JJ Boomsma: Thu army ant queens re-mate later in life? In: Insectes Sociaux 54, 2007, pp. 20-28, doi: 10.1007 / s00040-007-0904-2 .
  14. ^ Daniel JC Kronauer, Caspar Schöning, Patrizia d'Ettorre, Jacobus J. Boomsma: Colony fusion and worker reproduction after queen loss in army ants. In: Proceedings of the Royal Society Series B 277, 2010, pp. 755-763, doi: 10.1098 / rspb.2009.1591 .
  15. ↑ Sean G. Brady, Philip S. Ward: Morphological phylogeny of army ants and other dorylomorphs (Hymenoptera: Formicidae). In: Systematic Entomology 30, 2005, pp. 593-618, doi: 10.1111 / j.1365-3113.2005.00290.x .
  16. ^ Daniel JC Kronauer: Recent advances in army ant biology (Hymenoptera: Formicidae). In: Myrmecological News 12, 2009, pp. 51-65.
  17. ↑ AntWeb: Subfamiliy Dorylinae .
  18. ↑ a b William H. Gotwald: Phylogenetic implication of army ant zoogeography. In: Annals of the Entomological Society of America 72, No. 4, 1979, pp. 462-467.
  19. ^ Sean G. Brady: Evolution of the army ant syndrome: The origin and long-term evolutionary stasis of a complex of behavioral and reproductive adaptations. In: PNAS 100, No. 11, 2003, pp. 6575-6579, doi: 10.1073 / pnas.1137809100 .
  20. ^ Zheng-Hui Xu: Two new genera of ant subfamilies Dorylinae and Ponerinae (Hymenoptera, Formicidae) from Yunnan, China. In: Zoological Research 21, No. 4, 2000, pp. 297-302.
  21. ^ Marek L. Borowiec: New ant species related to Cerapachys sexspinus and discussion of the status of Yunodorylus (Hymenoptera: Formicidae). In: Zootaxa 2069, 2009, pp. 43-58.
  22. ^ Daniel JC Kronauer, Caspar Schöning, Lars B. Vilhelmsen, Jacobus J. Boomsma: A molecular phylogeny of Dorylus army ants provides evidence for multiple evolutionary transitions in foraging niche . In: BMC Evolutionary Biology . tape 7 , no. 1 , April 4, 2007, p. 56 , doi : 10.1186 / 1471-2148-7-56 , PMID 17408491 (open access).
  23. ^ Edward O. Wilson (1964): The true army ants of the Indo-Australian area. Pacific Insects 6 (3): 427-483.
  24. ^ CA Collingwood: Hymenoptera. Fam. Formicidae from Saudi Arabia. In: Fauna of Saudi Arabia 7, 1985, pp. 230-302.
  25. ↑ Donat Agosti, Cedric A. Collingwood: A provisional list of the Balkan ants (Hym. Formicidae) with a key to the worker caste. II. Key to the worker caste, including the European species without the Iberean. In: Mitteilungen der Schweizerische Entomologische Gesellschaft 60, 1987, pp. 261–293.
  26. ↑ C. Schöning, C. Csuzdi, W. Kinuthia, JO Ogutu (2010): Influence of driver ant swarm raids on earthworm prey densities in the Mount Kenya forest: implications for prey population dynamics and colony migrations. Insectes Sociaux 57: 73-82, doi: 10.1007 / s00040-009-0052-y
  27. ↑ Caspar Schöning & Mark W. Moffett (2007): Driver Ants Invading a Termite Nest: Why Do the Most Catholic Predators of All Seldom Take This Abundant Prey? Biotropica 39 (5): 663-667, doi: 10.1111 / j.1744-7429.2007.00296.x
  28. ↑ Peter H. Wrege, Martin Wikelski, James T. Mandel, Thomas Rassweiler, Iain D. Couzin (2005): Antbirds parasitize foraging army ants. Ecology, 86 (3): 555-559.
  29. ↑ Matthias Waltert, K. Serge Bobo, N. Moses Sainge, Heleen Fermon and Michael Muhlenberg. 2005. From forest to farmland: habitat effects on Afrotropical forest bird diversity. Ecological Applications 15: 1351-1366.
  30. ↑ Marcell K. Peters, Smith Likare, Manfred Krämer (2008): Effect of habitat fragmentation and degradation on flocks of African ant-following birds. Ecological Applications 18 (4): 847-858.
  31. ↑ Finn Gottrup & David Leaper (2004): Wound healing: Historical Aspects. EWMA Journal 4 (2): 21-26.
  32. ↑ John Bland-Sutton (1925): On faith in ligatures. British Medical Journal 1925 Nov. 7; 2 (3384): 823-826. PMC 2227635 (free full text)

Web links

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