Aenictus exilis

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Aenictus exilis
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Dorylinae
Genus: Aenictus
Species: A. exilis
Binomial name
Aenictus exilis
Wilson, 1964

Aenictus exilis casent0911128 p 1 high.jpg

Aenictus exilis casent0911128 d 1 high.jpg

Specimen Labels

Workers were found (in Karema) running in a very diffuse single file over the top of the ground and under leaf litter in a small, recently made clearing at the edge of virgin lowland rain forest. The time was noon of a sunny day (note that 3 colonies of the closely related Aenictus ceylonicus were found foraging in New Guinea between 9 and 11 in sunny mornings, or, in other words, at nearly the same time and under similar condition). The file was very inconspicuous and could not be traced more than a few feet. The Busu River workers were collected in a soil-litter berlesate from the floor of virgin lowland rain forest, in close company with such distinctive Papuan ant species as Dacetinops cibdelus, Strumigenys mayri, Eurhopalothrix biroi, and Eurhopalothrix brevicornis.

Identification

A member of the ceylonicus group.

Key to Aenictus species groups

Distribution

Distribution based on Regional Taxon Lists

Indo-Australian Region: New Guinea (type locality).

Distribution based on specimens

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The above specimen data are provided by AntWeb. Please see Aenictus exilis for further details

Biology

Little is known about the biology of Aenictus exilis. The genus is comprised of species that live an army ant lifestyle. Aenictus typically prey on other ants, from other genera, or other insects such as wasps or termites. There are reports of Aenictus preying on other insects as well and even have been observed collecting honeydew from homopterans (Santschi, 1933; Gotwald, 1995) but this appears, at least from available evidence, to be uncommon. Foraging raids can occur day or night across the ground surface. Occasionally raids are arboreal. During a raid numerous workers attack a single nest or small area, with several workers coordinating their efforts to carry large prey items back to the nest or bivouac. Aenictus have a nomadic life style, alternating between a migratory phase in which nests are temporary bivouacs in sheltered places above the ground and a stationary phase where semi-permanent underground nests are formed. During the nomadic phase bivouacs move regularly, sometimes more than once a day when larvae require large amounts of food. Individual nests usually contain up to several thousand workers, although nest fragments containing only a few hundred workers are often encountered. Queens are highly specialised and look less like workers than in most ant species. They have greatly enlarged gasters (dichthadiform) and remain flightless throughout their life. New colonies are formed by the division of existing colonies (fission) rather than by individual queens starting colonies on their own.

Castes

Known only from the worker caste.

Wilson 1964 Army Ant fig 31-36

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • exilis. Aenictus exilis Wilson, 1964a: 462, fig. 33 (w.) NEW GUINEA.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Description

Worker

Holotype: HW 0.40 mm, HL 0.48 mm, SL 0.31 mm. Antenna 10-segmented. Very similar to workers from sympatric series of ceylonicus (Mayr), differing chiefly in its smaller size, lighter coloration, and weaker sculpturing. (The name exilis means weak or feeble and refers to these characteristics). Mandibles thin and 4-toothed, as in ceylonicus. Cephalic structure as in ceylonicus. Propodeum angulate. Subpetiolar process large, consisting of a forward-directed lobe surmounted by a thin, acutely angulate flange which is directed straight downward. Pilosity moderately abundant; the length of the longest pronotal hairs only about 0.10 mm.

Head shining. Pronotum shining. Propodeal dorsum very weakly microreticulate, feebly shining. Meso-, metapleuron, and sides of propodeum longitudinally rugose, the interspaces weakly microreticulate and subopaque to feebly shining. Dorsa and most of sides of pedicel shining, the remainder weakly microreticulate and subopaque. Concolorus light brownish yellow.

Paratypes: 9 workers from same colony as holotype. Also, 2 workers from lower Busu River, Huon Peninsula, NE New Guinea, 14.V.1955 (Wilson, ace. no. 1052). HW of Karema workers 0.38-0.41 mm, of Busu River workers 0.37, 0.42 mm. The Busu River workers differ from holotype nest series in having propodeal dorsum strongly shining.

References

  • Jaitrong, W. & Yamane, S. 2011. Synopsis of Aenictus species groups and revision of the A. currax and A. laeviceps groups in the eastern Oriental, Indo-Australian, and Australasian regions (Hymenoptera: Formicidae: Aenictinae). Zootaxa, 3128, 1–46. PDF
  • Wilson, E. O. 1964a. The true army ants of the Indo-Australian area (Hymenoptera: Formicidae: Dorylinae). Pac. Insects 6: 427-483 (page 462, fig. 33 worker described)