Aenictus itoi

Aenictus itoi
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Dorylinae
Genus:	Aenictus
Species:	A. itoi
Binomial name
Aenictus itoi Jaitrong & Yamane, 2013

Known only from the type locality in a lowland rainforest.

Identification

A member of the ceylonicus group. This species can be separated from the other members by the subpetiolar process being developed, subtriangular, with its apex spiniform and directed downward. (Jaitrong and Yamane 2013)

Keys including this Species

• Key to southeastern Asian Aenictus ceylonicus group species

Distribution

W. Sumatra

Distribution based on Regional Taxon Lists

Indo-Australian Region: Indonesia (type locality).

Distribution based on AntMaps

Distribution based on AntWeb specimens

Check data from AntWeb

Countries Occupied

Number of countries occupied by this species based on AntWiki Regional Taxon Lists. In general, fewer countries occupied indicates a narrower range, while more countries indicates a more widespread species.

Estimated Abundance

Relative abundance based on number of AntMaps records per species (this species within the purple bar). Fewer records (to the left) indicates a less abundant/encountered species while more records (to the right) indicates more abundant/encountered species.

Biology

Explore Overview of Aenictus biology  Little is known about the biology of Aenictus itoi. 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 Online Catalogue of the Ants of the World.

• itoi. Aenictus itoi Jaitrong & Yamane, 2013: 192, fig. 21A-C (w.) INDONESIA (Sumatra).
  • Type-material: holotype worker, 4 paratype workers.
  • Type-locality: holotype Indonesia: Sumatra, Padang, Sukarami, 1-5.i.1992, F192-25 (F. Ito); paratypes with same data.
  • Type-depositories: MZBJ (holotype); SKYC, TNHM (paratypes).
  • Distribution: Indonesia (Sumatra).

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

Description

Worker

(Holotype and paratype workers, n = 5). TL 2.75–3.00 mm; HL 0.58–0.61 mm; HW 0.58–0.63 mm; SL 0.46–0.53 mm; ML 0.88–0.98 mm; PL 0.20–0.25 mm; CI 100–102; SI 80–88.

Head in full-face view round, almost as long as broad, sides and posterior margin convex; occipital margin bearing a carina. Antennal scape relatively short, reaching only 2/3 of head length. Frontal carina relatively short, recahing the level of posterior margin of torulus. Parafrontal ridge incomplete or almost absent. Anterior clypeal margin concave, concealed by curved anterior extension of frontal carina. Masticatory margin of mandible with a large acute apical tooth followed by a medium-sized subapical tooth, 5 denticles, and a medium-sized basal tooth; basal margin concave. Maximum width of gap between anterior clypeal margin and mandibles about 1.8 times as broad as maximum width of mandible. Promesonotum convex dorsally and sloping gradually to metanotal groove; mesopleuron relatively long, not clearly demarcated from metapleuron; metapleural gland bulla relatively small, its maximum diameter as long as distance from propodeal spiracle to metapleural gland bulla. Propodeum in profile with straight dorsal outline; propodeal junction nearly right-angled; declivity of propodeum seen from back widely and shallowly concave, encircled with a rim. Petiole almost as long as high, with its dorsal outline elevated posteriorly; subpeiolar process subtriangular, anteroventrally not angulate, its apax directed downward. Postpetiole almost as long as petiole but slightly narrower than petiole, seen in profile with its dorsal outline elevated posteriorly.

Head including antennal scape and gaster entirely smooth and shiny. Mandible very finely striate. Promesonotum smooth and shiny except for anteriormost part punctate; mesopleuron, metapleuron, lateral face of propodeum wrinkled; propodeal dorsum reticulate; petiole densely punctate; lateral face of postpetipole superficially reticulate, postpetiolar dorsum smooth and shiny.

Head and mesosoma dorsally with relatively dense standing hairs; longest pronotal hair 0.18–0.20 mm long. Head, petiole, gaster, and legs yellowish brown; mesosoma reddish brown.

Type Material

Holotype. INDONESIA: Worker from W. Sumatra, Padang, Sukarami, 1–5.I.1992, leg. F. Ito, FI92-25 (MZB). Paratypes. Four workers, same data as holotype (SKYC, THNHM).

Etymology

The specific name is dedicated to Professor Dr. Fuminori Ito of Kagawa University (Japan), who donated the type series to us.

References

• Antony, A.K., Prasad, G. 2022. Two new species of army ants of the Aenictus ceylonicus group (Hymenoptera: Formicidae) from Kerala, India. Journal of Threatened Taxa 14(3): 20780-20785 (doi:10.11609/jott.6962.14.3.20780-20785).
• Dhadwal, T., Bharti, H. 2023. Aenictus dirangensis sp. nov. (Hymenoptera: Formicidae), a new species of Aenictus ceylonicus group from India. Journal of the Entomological Research Society 25(2): 387-403 (doi:10.51963/jers.v25i2.2367).
• Jaitrong, W. & Yamane, S. 2013. The Aenictus ceylonicus species group (Hymenoptera, Formicidae, Aenictinae) from Southeast Asia. Journal of Hymenoptera Research 31:165-233.

References based on Global Ant Biodiversity Informatics

• Borowiec M. L. 2016. Generic revision of the ant subfamily Dorylinae (Hymenoptera, Formicidae). ZooKeys 608: 1–280.
• Chapman J. W. 1965. Studies on the ecology of the army ants of the Philippines genus Aenictus Schuckard (Hymenoptera: Formicidae). Philippine Journal of Science. 93: 551-595.
• Jaitrong W., and S. Yamane. 2013. The Aenictus ceylonicus species group (Hymenoptera, Formicidae, Aenictinae) from Southeast Asia. Journal of Hymenoptera Research 31: 165-233.