Aenictus longicephalus

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

Known only from the type locality located in Lombok, east side of Wallace’s line.

Identification

A member of the ceylonicus group. Jaitrong and Yamane (2013) – Aenictus longicephalus is most similar to Aenictus minipetiolus from Lombok as they share the declivity of propodeum slightly convex, with blunt lateral carinae but not demarcated basally by a transverse carina, and smooth and shiny mesosomal dorsum. However, A. longicephalus is easily separated from A. minipetiolus by the following characteristics: propodeal junction rounded (angulate, right-angled in the latter); basal margin of mandible almost straight (distal 2/3 straight, proximal 1/3 sloping gradually to mandibular base in the latter); petiole larger than postpetiole (smaller than postpetiole in the latter).

Keys including this Species

Key to southeastern Asian Aenictus ceylonicus group species

Distribution

Lombok

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 longicephalus. 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.

longicephalus. Aenictus longicephalus Jaitrong & Yamane, 2013: 199, fig. 12A-C (w.) INDONESIA (Lombok).
- Type-material: holotype worker, 14 paratype workers.
- Type-locality: holotype Indonesia: Lombok, nr Semaya, Kopi house, 26.x.1998, Eg98-LMB-1041 (K. Eguchi); paratypes with same data.
- Type-depositories: MZBJ (holotype); BMNH, MCZC, SKYC, TNHM (paratypes).
- Distribution: Indonesia (Lombok).

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 2.00–2.35 mm; HL 0.43–0.55 mm; HW 0.35–0.45 mm; SL 0.23–0.33 mm; ML 0.55–0.70 mm; PL 0.18–0.20 mm; CI 82–83; SI 64–76.

Head in full-face view distinctly longer than broad, sides weakly convex, posterior margin almost straight; occipital margin bearing a distinct carina. Antennal scape relatively short, reaching only 1/2 of head length. Frontal carina relatively very short and indistinct, not reaching the level of posterior margin of torulus. Parafrontal ridge feeble and incomplete. Anterior clypeal margin almost straight or feebly concave, not concealed by curved anterior extension of frontal carina. Masticatory margin of mandible with large acute apical tooth followed by a medium-sized subapical tooth, 2 denticles, and a medium-sized basal tooth; basal margin almost straight. Maximum width of gap between anterior clypeal margin and mandibles about 1.8 times as broad as maximum width of mandible. Promesonotum weakly convex dorsally and sloping gradually to propodeal junction; metanotal groove evanescent; mesopleuron relatively long, demarcated from metapleuron by indistinct groove; metapleural gland bulla relatively large, its maximum diameter about 1.6 times as long as distance between propodeal spiracle and metapleural gland bulla.

Propodeum in profile with feebly convex dorsal outline; propodeal junction rounded; declivity of propodeum slightly convex, with blunt lateral carinae but not demarcated basally by a transverse carina. Petiole almost as long as high, with its dorsal outline convex; subpetiolar process low and subrectangular. Postpetiole slightly smaller than petiole, with its dorsal outline roundly convex.

Head including antennal scape entirely smooth and shiny. Mandible very finely striate. Mesosomal dorsum entirely smooth and shiny; mesopleuron reticulate; metapleuron and lateral face of propodeum wrinkled. Petiole entirely smooth and shiny except lower portion reticulate; postpetiole entirely smooth and shiny.

Head and mesosoma dorsally with relatively dense decumbent hairs; longest pronotal hair 0.08–0.10 mm long (slightly shorter than petiolar hairs). Head including mandible and mesosoma reddish brown; petiole, postpetiole, gaster, antenna, and legs yellow to yellowish brown.

Type Material

Holotype. INDONESIA: Worker from W. Lombok, nr. Semaya, Kopi house, 26.X.1998, leg. K. Eguchi, Eg98-LMB-1041 (MZB). Paratypes. Fourteen workers, same data as holotype (BMNH, MCZC, SKYC, THNHM).

Etymology

Specific epithet “longicephalus” is a Latin meaning “long-headed”.

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.
Jaitrong W., and S. Yamane. 2013. The Aenictus ceylonicus species group (Hymenoptera, Formicidae, Aenictinae) from Southeast Asia. Journal of Hymenoptera Research 31: 165-233.