Aenictus biroi

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Aenictus biroi
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Dorylinae
Genus: Aenictus
Species: A. biroi
Binomial name
Aenictus biroi
Forel, 1907

Aenictus biroi casent0905989 p 1 high.jpg

Aenictus biroi casent0905989 d 1 high.jpg

Specimen Labels

The type colony was "in a bare area, [from] a very populous nest excavated in hard clay soil."


Jaitrong et al. (2010) - A member of the wroughtonii group. This species is similar to Aenictus camposi in the angulate propodeal junction, dense punctuation on mesothorax and propodeum, and unarmed subpetiolar process. In A. biroi, However, the body is slightly larger than in A. composi, and the head is almost as long as broad (in the latter the head is clearly longer than broad), and the declivity of the propodeum is broader and widely rounded above (in the latter it is narrow and distinctly tapers above).

Keys including this Species


Latitudinal Distribution Pattern

Latitudinal Range: 6.8498° to 6.8498°.

Tropical South

Distribution based on Regional Taxon Lists

Oriental Region: Sri Lanka (type locality).

Distribution based on AntMaps


Distribution based on AntWeb specimens

Check data from AntWeb


Little is known about the biology of Aenictus biroi. 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.


Wilson 1964 Army Ant fig 64-75


The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

  • biroi. Aenictus biroi Forel, 1907a: 10 (w.) SRI LANKA.
    • Type-material: lectotype worker (by designation of Jaitrong, et al. 2010: 37), 3 paralectotype workers.
    • Type-locality: lectotype Sri Lanka (“Ceylon”): Pattipola, 2000 m. (L. Biró); paralectotypes with same data.
    • Type-depository: MHNG.
    • [Note: 1 original syntype worker in NHMB, probably others in HNHM.]
    • Status as species: Emery, 1910b: 29; Chapman & Capco, 1951: 10; Wilson, 1964a: 451; Bolton, 1995b: 59; Jaitrong, et al. 2010: 37 (redescription); Jaitrong & Ruangsittichai, 2018: 113 (in key).
    • Distribution: Sri Lanka.

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



Wilson (1964) - (Syntype: HW 0.59 mm, HL 0.70 mm, SL 0.67 mm. Antenna 10-segmented. Mandible typical. Clypeus convex, entire, unarmed. Parafrontal ridge indistinct, only 0.15 mm long. Basal face of propodeum seen from side strongly convex. Propodeal junction right-angular. Subpetiolar process a low lobe located beneath anterior 1/2 of node. Pilosity relatively sparse and short; length of longest pronotal hairs only 0.10 mm.

Head shining. Mesopleuron and propodeum microreticulate and opaque; remainder of mesosoma shining. Pedicel shining.

Jaitrong et al. (2010) - Measurements. Worker lectotype and paralectotypes (n = 4): TL 3.1-3.2 mm; HL 0.60-0.65 mm; HW 0.50 mm; SL 0.63-0.65 mm; ML 1.08 mm; MTL 0.63-0.65 mm; PL 0.23-0.25 mm, CI 85; SI 114-118.

Head in full-face view slightly longer than broad, with its sides and posterior margin roundly convex: posterolateral corner round. Antennal scape long, almost as long as head length; antennal segment II nearly as long as III; IV-VI almost the same in length, and each slightly shorter than III; VII-IX each slightly longer and broader than VI; the last (X) almost as long as VIII and IX combined. Frontal carina well developed, thin and extending: posteriorly beyond the level of posterior margin of torulus: seen in profile its dorsal outline concave in the middle. Clypeus short, slightly protruding anteriad, with its anterior margin almost straight, bearing 6-8 denticles. Mandible with the apical tooth large and curved, followed by a series of 8-10 minute teeth on masticatory margin. Mesosoma relatively thick, seen from above broader ventrally and constricted at mesothorax: in profile pronotum convex dorsally and sloping gradually to metanotal groove; mesopleuron clearly demarcated from metapleuron by a ridge: upper portion of mesopleuron slightly impressed. Propodeum in profile lower than promesonotum, with nearly straight dorsal outline that slopes down posteriad: area below spiracle impressed, propodeal junction angulate; declivity of propodeum widely and shallowly concave encircled with a thin rim. Petiole slightly longer than high, elevated posteriorly; subpetiolar process present; its ventral outline strongly convex, without angle or tooth: postpetiolar node short, almost as long as broad.

Head and antennal scape smooth and shiny. Pronotum smooth and shiny, with its anteriormost portion punctate; mesothorax and propodeum with dense punctures; propodeal dorsum with short longitudinal rugae along the angle. Petiole extensively smooth and shiny, with its anteriormost part sparsely punctate: postpetiole almost smooth and shiny. Gaster, femora and tibiae smooth and shiny.

Body with relatively sparse standing hairs mixed with sparse short hairs over the surface; length of the longest pronotal hair 0.18-0.20 mm. Head, waist, gaster, antenna and legs yellow: mesosoma pale brown.

Type Material

Jaitrong et al. (2010) - Four syntype workers (one on a pin, three on another) from Pattipola (2,000 m), Ceylon [Sri Lanka] (Musee d'Histoire Naturelle Genève, examined). The single specimen mounted on one pin is selected as the lectotype, the others as paralectotypes.


  • Forel, A. 1907d. Formicides du Musée National Hongrois. Ann. Hist.-Nat. Mus. Natl. Hung. 5: 1-42 (page 10, worker described)
  • Jaitrong, W., Yamane, S. & 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. & 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 451, see also)

References based on Global Ant Biodiversity Informatics

  • Baroni Urbani C. 1977. Katalog der Typen von Formicidae (Hymenoptera) der Sammlung des Naturhistorischen Museums Basel (2. Teil). Mitt. Entomol. Ges. Basel (n.s.) 27: 61-102.
  • Dias R. K. S. 2002. Current knowledge on ants of Sri Lanka. ANeT Newsletter 4: 17- 21.
  • Dias R. K. S. 2006. Current taxonomic status of ants (Hymenoptera: Formicidae) in Sri Lanka. The Fauna of Sri Lanka: 43-52. Bambaradeniya, C.N.B. (Editor), 2006. Fauna of Sri Lanka: Status of Taxonomy, Research and Conservation. The World Conservation Union, Colombo, Sri Lanka & Government of Sri Lanka. viii + 308pp.
  • Dias R. K. S. 2013. Diversity and importance of soil-dweeling ants. Proceedings of the National Symposium on Soil Biodiversity, chapt 4, pp 19-22.
  • Dias R. K. S., K. R. K. A. Kosgamage, and H. A. W. S. Peiris. 2012. The Taxonomy and Conservation Status of Ants (Order: Hymenoptera, Family: Formicidae) in Sri Lanka. In: The National Red List 2012 of Sri Lanka; Conservation Status of the Fauna and Flora. Weerakoon, D.K. & S. Wijesundara Eds., Ministry of Environment, Colombo, Sri Lanka. p11-19.
  • Emery C. 1910. Hymenoptera. Fam. Formicidae. Subfam. Dorylinae. Genera Insectorum 102: 1-34.
  • Forel A. 1907. Formicides du Musée National Hongrois. Ann. Hist.-Nat. Mus. Natl. Hung. 5: 1-42.
  • Jaitrong W.; Yamane, S.; Wiwatwitaya, D. 2010. The army ant Aenictus wroughtonii (Hymenoptera, Formicidae, Aenictinae) and related species in the Oriental region, with descriptions of two new species. Japanese Journal of Systematic Entomology 16:33-46.
  • Wilson E. O. 1964. The true army ants of the Indo-Australian area (Hymenoptera: Formicidae: Dorylinae). Pacific Insects 6: 427-483.