Aenictus longicephalus

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).

Key to Aenictus species groups / Key to southeastern Asian Aenictus ceylonicus group species

Distribution
Lombok

Distribution based on Regional Taxon Lists
Indo-Australian Region: Indonesia.

Castes
Known only from the worker caste.

Nomenclature

 *  longicephalus. Aenictus longicephalus Jaitrong & Wiwatwitaya, 2013: 199, figs. 12A-C (w.) INDONESIA.

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”.