Aenictus concavus

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

Known only in from the lowlands. The type series was collected in a wet evergreen forest near a stream. A colony from Khao Yai National park was collected in a bamboo forest.

Identification

A member of the ceylonicus group. Jaitrong and Yamane (2013) - Aenictus concavus is separated from the other species of the group by the following characteristics: head in profile relatively flattened with occipital corner convex bearing a distinct protuberance, in full-face view with posterior margin strongly concave (occipital corner round in the other species except A. gonioccipus); promesonotum almost flat or feebly convex dorsally. The single specimen collected from Cat Tien National Park (Eg04-VN-526) is extremely similar to the type series in all characters except for slightly more developed sculpture on mesopleuron, metapleuron, and propodeum and a slightly more angulated propodeal junction.

Keys including this Species

Key to southeastern Asian Aenictus ceylonicus group species

Distribution

Distribution based on Regional Taxon Lists

Oriental Region: Thailand (type locality), Vietnam.

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 concavus. 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.

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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.

concavus. Aenictus concavus Jaitrong & Yamane, 2013: 178, fig. 4A-C (w.) THAILAND, VIETNAM.
- Type-material: holotype worker, 9 paratype workers.
- Type-locality: holotype Thailand: Chanthaburi Prov., Pong Nam Ron Dist., Hin Dad Waterfall, 15.v.2008, WJT08-E094 (W. Jaitrong); paratypes with same data.
- Type-depositories: TNHM (holotype); SKYC, TNHM (paratypes).
- Status as species: Khachonpisitsak, et al. 2020: 25.
- Distribution: Thailand, Vietnam.

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 paratypes, n = 7). TL 2.20–2.30 mm; HL 0.54–0.56 mm; HW 0.48–0.50 mm; SL 0.33–0.35 mm; ML 0.75–0.78 mm; PL 0.20–0.25 mm; CI 84–89; SI 68–70.

Head in full-face view clearly longer than broad, with anterior portion narrower than posterior portion, sides convex, posterior margin strongly concave; with head in profile occipital corner convex, with a distinct protuberance on occipital corner; occipital margin bearing a distinct carina. Antennal scape relatively short, not reaching 2/3 of head length. Frontal carinae relatively short, fused at the level of antennal base to form a single carina, reaching the level of posterior margin of torulus. Parafrontal ridge feeble and incomplete. Anterior clypeal margin strongly concave, concealed by curved anterior extension of frontal carinae. Masticatory margin of mandible with 3 teeth including a large apical tooth; basal margin convex. Maximum width of gap between anterior clypeal margin and mandibles about 3.3 times as broad as maximum width of mandible. Promesonotum almost flat or feebly convex dorsally; metanotal groove indistinct; mesopleuron relatively short, demarcated from metapleuron by an indistinct groove; metapleural gland bulla relatively large, its maximum diameter 3 times as long as distance between propodeal spiracle and metapleural gland bulla. Propodeum in profile with feebly convex dorsal outline; propodeal junction bluntly angulate; declivity of propodeum widely and shallowly concave, encircled with a distinct rim. Petiole slightly longer than high, with its dorsal outline convex; subpetiolar process weakly developed, its anteroventral corner acutely angulate and ventral outline almost straight or feebly concave. Postpetiole distinctly shorter than petiole, subrectangular.

Head including mandible and antennal scape entirely smooth and shiny. Promesonotum smooth and shiny except for anteriormost portion reticulate; mesopleuron, metapleuron, and propodeum reticulate; in addition mesopleuron and metapleuron with relatively irregular longitudinal rugae; petiole and postpetiole reticulate except dorsa smooth and shiny. Legs entirely smooth and shiny.

Head with relatively sparse standing hairs mixed with dense short hairs over surface; mesosoma dorsally with relatively sparse standing hairs mixed with sparse decumbent hairs; longest pronotal hair 0.15–0.18 mm long. Head, mesosoma, petiole, and postpetiole reddish brown; gaster and legs yellowish brown.

Type Material

Holotype. THAILAND: Worker from E. Thailand, Chanthaburi Prov., Pong Nam Ron Dist., Hin Dad Waterfall, 15.V.2008, leg. W. Jaitrong, WJT08-E094 (THNHM). Paratypes. Nine workers, same data as holotype (SKYC, THNHM)

Etymology

The specific name refers to the strongly concave vertex of the head.

References

References based on Global Ant Biodiversity Informatics

Borowiec M. L. 2016. Generic revision of the ant subfamily Dorylinae (Hymenoptera, Formicidae). ZooKeys 608: 1–280.
Huong N. T. T., P. V. Sang, and B. T. Viet. 2015. A preliminary study on diversity of ants (Hymenoptera: Formicidae) at Hon Ba Nature Reserve. Environmental Scientific Conference 7: 614-620.
Jaitrong W. 2015. A revision of the Thai species of the ant genus Aenictus Shuckard, 1840 (Hymenoptera: Formicidae: Dorylinae). The Thailand Natural History Museum Journal 9(1): 1-94.
Jaitrong W., and S. Yamane. 2013. The Aenictus ceylonicus species group (Hymenoptera, Formicidae, Aenictinae) from Southeast Asia. Journal of Hymenoptera Research 31: 165-233.