Aenictus stenocephalus

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Aenictus stenocephalus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Dorylinae
Genus: Aenictus
Species: A. stenocephalus
Binomial name
Aenictus stenocephalus
Jaitrong & Yamane, 2010

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The type specimens were collected with pitfall traps in a natural forest (dry evergreen forest and grassland), and non-type specimens from an agricultural area near a natural forest in northeastern Thailand. (Jaitrong et al. 2010)

Identification

Jaitrong et al. (2010) - A member of the wroughtonii group. This species is easily distinguished from other species of the group by the almost entirely smooth and shiny body together with angulate propodeal junction. The other important characteristics are the exceptionally narrow head with long antennal scape, subrectangular petiole, only weakly convex pronotum, and almost rudimentary subpetiolar process (but with an acutely angulate anteroventral corner).

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Oriental Region: Thailand (type locality).

Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Little is known about the biology of Aenictus stenocephalus. 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.

Nomenclature

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

  • stenocephalus. Aenictus stenocephalus Jaitrong & Yamane, in Jaitrong, et al. 2010: 41, figs. 13-15 (w.) THAILAND.

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

Description

Worker

Holotype, three paratype, and one non-type workers (n = 5): TL 3.0-3.1 mm; HL 0.55-0.58 mm; HW 0.48 mm; SL 0.63-0.65 mm; ML 1.00-1.03 mm; MTL 0.65-0.68 mm; PL 0.23-0.25 mm; CI 83-86; SI 132-137.

Head un full-face view narrow, elliptical, distinctly longer than broad, with slightly convex sides and posterior margin of head. Antennal scape long, extending beyond the posterior margin of head (SI 132-137): antennal segment II slightly shorter than III and as long as IV or more: V-VII combined as long as VIII and IX combined and almost as long as the last segment (X). Frontal carina short and thin, not extending beyond the level of posterior margin of torulus. Clypeus short, with very slightly convex anterior margin that bears 8-10 teeth. Mandible with the apical tooth large and curved, followed by 10-12 minute teeth on masticatory margin. Mesosoma elongate; in profile pronotum weakly convex dorsally; promesonotum sloping gradually to metanotal groove. Propodeum slightly lower than promesonotum with its dorsal outline almost straight in profile; propodeal junctionion angulate; declivity of propodeum widely and shallowly concave. encircled with a thin rim. Petiole large, seen in profile subrectangular, slightly longer than high and almost straight dorsally; subpetiolar process weakly developed with its ventral outline feebly convex, and anteroventral corner acutely angulate; postpetiole slightly smaller than petiole, with its node rounded above and scarcely longer than broad.

Head and antennal scape smooth and shiny. Pronotum smooth and shiny, with its anteriormost portion punctate; mesothorax and metapleuron with dense microrecticulae; propodeum extensively smooth and shiny; propodeal declivity entirely sculptured; in the area in front of the angle with fine sculpture. Petiole smooth and shiny, with its anteriormost part sparsely punctate; postpetiole also extensively smooth and shiny. Gaster, and femora and tibiae of legs smooth and shiny.

Body with relatively sparse standing hairs mixed with sparse short hairs over the surface: length of the longest pronotal hair 0.15-0.18 mm. Head, waist, gaster, antenna and legs yellow or pale brown: mesosoma dark brown.

Type Material

Holotype worker from agricultural area, new Phu Kheao W. S., Chaiyaphum Prov., NE. Thailand, 30 I 1999, W. Jaitrong leg., WJT99-AG20. Three paratype workers, same data as Holotype. Holotype and one paratype is deposited in Natural History Museum of the National Science Museum, one paratype in SKY Collection, and the other in Ant Museum.

Etymology

The specific epithet “stenocephalus” is Latin meaning “narrow-headed”.

References

  • Jaitrong, W., Yamane, S. and Wiwatwitaya, D. 2010. The Army Ant Aenictus wroughtonii and related species in the Oriental region, with descriptions of two new species. Japanese Journal of Systematic Entomology. 16:33-36. PDF.
  • Jaitrong, W. and 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