Aenictus cornutus

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Aenictus cornutus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Dorylinae
Genus: Aenictus
Species: A. cornutus
Binomial name
Aenictus cornutus
Forel, 1900

Aenictus cornutus casent0249267 p 1 high.jpg

Aenictus cornutus casent0249267 d 1 high.jpg

Specimen Labels

All colonies of this species have been collected from lowland rainforests. Rościszewski and Maschwitz (1994) reported that in the Pasoh Forest Reserve, Malaysia, Aenictus cornutus foraged on the ground and feed on ants of the genera Polyrhachis and Technomyrmex. (Jaitrong and Yamane 2011)

Identification

This species is easily distinguished from the other members of the currax group as follows: pronotum armed with large bilateral horn-like protuberances; antennal scape, legs and postpetiole distinctly punctate.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Indo-Australian Region: Borneo (type locality), Indonesia, Malaysia.

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 cornutus. 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.

  • cornutus. Aenictus cornutus Forel, 1900b: 75 (w.) BORNEO. See also: Wilson, 1964a: 457; Jaitrong & Yamane, 2011: 11.

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

Description

Worker

Wilson 1964 Army Ant fig 21-30

Jaitrong and Yamane (2011) - Measurements. lectotype and paralectotypes (n = 4): TL 4.00–4.45 mm; HL 0.83–0.88 mm; HW 0.73–0.78 mm; SL 0.80–0.88 mm; ML 1.48–1.55 mm; PL 0.35–0.38 mm; CI 86–89; SI 107–114.

(lectotype and paralectotypes). Head in full-face view clearly longer than broad, with sides slightly convex and posterior margin sinuate; occipital margin bearing a narrow collar. Antenna relatively thick; scape not reaching posterolateral corner of head; antennal segments II–VI slightly longer than broad, of approximately same length; VII–IX thicker and slightly longer; X slightly longer than VIII+IX. Frontal carina short, slightly extending beyond the level of posterior margin of torulus and well developed anteriorlly. Parafrontal ridge short and bluntly pointed at apex. Masticatory margin of mandible with a large apical tooth followed by a medium-sized subapical tooth and 5–6 denticles; basal margin of mandible lacking denticles. Mesosoma slender; pronotum anteriorly armed with large bilateral horn-like protuberances, a unique character within the species group. Propodeum in profile with weakly convex dorsal outline; propodeal junction angular; declivity of propodeum shallowly concave, and encircled with a thin rim. Petiole distinctly longer than high, with its dorsal outline elevated posteriorlly; subpetiolar process low, with its anteroventral corner angulate, and ventral margin almost straight, sometimes with lamellate lower portion. Postpetiole distinctly longer than high, with its dorsal outline convex.

Head entirely smooth and shiny. Mandible very finely striate except for masticatory and outer zones. Antennal scape punctate. Pronotum smooth and shiny except for the anteriormost portion and pronotal horns which are punctate; mesothorax, metapleuron, and propodeum with dense punctures and bearing several longitudinal rugulae.

Petiole and postpetiole densely punctate as are metathorax and propodeum. Legs densely punctate. Head and mesosoma dorsally with relatively sparse long standing hairs mixed with dense short hairs; longest pronotal hair 0.35 mm long. Entire body dark reddish-brown. Typhlatta spot located at the occipital corner.

Type Material

Jaitrong and Yamane (2011) - Four syntype workers (two on each of the two pins) from Borneo, Sarawak (Musee d'Histoire Naturelle Genève, examined). One worker among them (bottom on a pin) is selected as the lectotype, the others as paralectotypes.

References

  • Forel, A. 1900. Ponerinae et Dorylinae ď Australie. Récoltés par MM. Turner, Froggatt, Nugent, Chase, Rothney, J.-J. Walker, etc. Annales de la Société Entomologique de Belgique, 44, 54–77. (page 75, worker described)
  • 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
  • Terayama, M.; Yamane, S. 1989. The army ant genus Aenictus (Hymenoptera, Formicidae) from Sumatra, with descriptions of three new species. Jpn. J. Entomol. 57: 597-603 (record in Sumatra)
  • Wilson, E. O. 1964a. The true army ants of the Indo-Australian area (Hymenoptera: Formicidae: Dorylinae). Pacific Insects. 6: 427-483 (page 457, see also)