Dark guest ant (Anergates atratulus)

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Male dark guest ant
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Dark guest ant fact file

Dark guest ant description

KingdomAnimalia
PhylumArthropoda
ClassInsecta
OrderHymenoptera
FamilyFormicidae
GenusAnergates (1)

A highly specialised parasite with a remarkable life history, the dark guest ant (Anergates atratulus) not only takes over the nest of another ant species, but also enslaves its workers (3) (4). Male dark guest ants are cream to yellow in colour and similar to pupae in appearance, being wingless and barely able to walk (4). Queen dark guest ants are tiny and winged (5) and normally have an abdomen greatly swollen with eggs when found in the host nest (4). Both the queen and the male dark guest ant are greatly reduced in size in comparison to non-parasitic ant species (3).

The scientific name of this species, Anergates, derives from the Greek words meaning ‘no’ and ‘workers’, referring to the fact that, unlike most other ant species, there are no worker ants (wingless, sterile females). Instead there are just males and gynes (females destined to become queens) (3) (4).

Size
Male length: 2 - 5 mm (2)
Female length: 2 - 3 mm (2)
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Dark guest ant biology

Unlike most ant species, the dark guest ant is not able to produce worker ants, those individuals that are responsible for searching for food and caring for the brood. This means that the only way this particular ant can survive is by enslaving the worker ants of another species, Tetramorium ceaspitum (known as the ‘pavement ant’, due to it frequently nesting in pavement cracks) (3) (5).

The dark guest ant is an extreme example of an ‘inquiline’, that is, an animal that lives in the nest or burrow of another species. A queen dark guest ant, which has just mated, invades a Tetramorium ceaspitum colony and becomes the new queen (3) (4). It is not clear whether the female achieves this position by taking over an old, queenless colony, or by influencing the Tetramorium ceaspitum workers to kill or starve their own queen (8). The loss of the Tetramorium ceaspitum queen means that no more host workers are produced, and because the dark guest ant now relies on these to survive, the dark guest ant colony can only exist for as long as the worker colony does, typically for two to five years. The queen, which is now swollen with eggs, reproduces quickly in order to secure the next generation (8).

The Tetramorium ceaspitum workers now forage for food for the new queen and her brood as if they were their own. These workers are predators and scavengers of animal and plant material, in particular seeds (8).

As the male dark guest ants are wingless, pupa-like and unable to leave the nest to find unrelated females, they mate with their female siblings in the nest (5). After mating, the females fly out of the nest in search of a new Tetramorium ceaspitum nest to invade (9)

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Dark guest ant range

The dark guest ant is native to Western Europe but it has also been accidentally introduced into North America, where it is now found along the Atlantic seaboard. It has had a recent population expansion into central North America, including Colorado (6).

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Dark guest ant habitat

The dark guest ant is found in grassland, heathland, and rocky and coastal areas. It generally prefers habitats with sparse vegetation cover and short, dry, acidic turf (7).

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Dark guest ant status

The dark guest ant is classified as Vulnerable (VU) on the IUCN Red List (1).

IUCN Red List species status – Vulnerable

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Dark guest ant threats

Known threats to the dark guest ant include loss of habitat through agricultural and coastal development. Afforestation and changes in grazing practices which result in vegetation growth also threaten the dark guest ant because it thrives in areas with little vegetation (7).

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Dark guest ant conservation

There are currently no known direct conservation measures in place for the dark guest ant; however, it has been found in nature reserves and indirectly gains protection through this (7).

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Find out more

To learn more about the conservation of ants and other insects see:

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Authentication

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

This species information was authored as part of the ARKive and Universities Scheme.
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Glossary

Afforestation
The establishment of forest by natural succession or by the planting of trees on land where they did not grow formerly.
Parasite
An organism that derives its food from, and lives in or on, another living organism at the host’s expense.
Pupae
Stage in an insect’s development when huge changes occur, which reorganise the larval form into the adult form.
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References

  1. IUCN Red List (October, 2010)
    http://www.iucnredlist.org/
  2. Donisthorpe, H. (1915) British Ants, their Life-History and Classification. G. Routledge and Sons, London.
  3. Holldobler, B. and Wilson, E.O. (1990) The Ants. The Belknap Press of Harvard University Press, Cambridge, Massachusetts.
  4. Fisher, B.L. and Cover, S.P. (2007) Ants of North America: A Guide to the Genera. University of California Press, Berkeley, California.
  5. Lubbock, J. (1881) Ants, Bees, and Wasps. Kegan Paul, London.
  6. Dash, S.T. and Sanchez, L. (2009)New distribution record for the social parasitic ant Anergates Atratulus (Schenck, 1852) (Hymenoptera: Formicidae): an IUCN Red-Listed species. Western North American Naturlist, 69(1): 140-141.
  7. UK Biodiversity Action Plan - Anergates atratulus (October, 2010)
    http://www.ukbap.org.uk/UKPlans.aspx?ID=96
  8. Edwards, R. and Telfer, M.G. (Eds.) (2002) Provisional Atlas of the Aculeate Hymenoptera of Britain and Ireland. Part 4. Biological Records Centre, Huntingdon.
  9. Wheeler, W.M. (1910) Ants: their Structure, Development and Behavior. Columbia University Press, New York.
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Image credit

Male dark guest ant  
Male dark guest ant

© Claude Pilon

Claude Pilon
claudepilon@cooptel.qc.ca
http://entomofaune.qc.ca/

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