Aenictus fulvus

Aenictus fulvus is probably a Sundaland species. We found a colony in a rubber tree plantation in southern Thailand (type series). Elsewhere it has been collected mostly in lowland primary rainforests. The type series was found under a large rotting log during the wet season; no worker activity was seen around the log and no immatures were found in the bivouac. The colony was preying on ants from the genus Crematogaster. (Jaitrong and Yamane 2011)

Identification
A member of the laeviceps species group. Jaitrong and Yamane (2011) - A. fulvus is quite similar to Aenictus alticola and Aenictus luzoni in having a slender body with the surface almost smooth and shiny. Compared with these species, A. fulvus is much smaller (HW 0.53–0.65 mm in A. fulvus; 0.80– 0.85 mm in A. alticola; 0.78 mm in A. luzoni) and has a low subpetiolar process without anterior angle, and ventrally with a spiniform appendage directed downward and backward (in A. alticola and A. luzoni the subpetiolar process is low and anteriorly angulate with the ventral appendage not spiniform). The workers of three colonies from Ulu Gombak, Malay Peninsula (FI92MG-651, VW-04, and VW-03) are brighter than in the type series from Khao Nan National Park, southern Thailand. The size variation occurs among individuals from single colonies.

Distribution
Malay Peninsula (S. Thailand and W. Malaysia), and Borneo (Sabah, Sarawak, Brunei, and E. Kalimantan)

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Malaysia. Oriental Region: Thailand.

Castes
Known only from the worker caste.

Nomenclature

 *  fulvus. Aenictus fulvus Jaitrong & Yamane, 2011: 34, figs. 28-30 (w.) THAILAND.

Worker
Measurements. Holotype and paratypes (n = 10): TL 2.95–3.10 mm; HL 0.63–0.75 mm; HW 0.53–0.65 mm; SL 0.48–0.60 mm; ML 0.90–1.05 mm; PL 0.23–0.25 mm; CI 84–87; SI 90–92.

holotype and paratypes - Head in full-face view subrectangular, much longer than broad, with sides rather parallel or feebly convex and posterior margin almost striaght; occipital carina complete. Antennal scape relatively short, not reaching posterolateral corner of head; antennal segments II–X each longer than broad; II almost as long as each of III–VII. Frontal carina very short, not extending beyond posterior margin of torulus. Anterior margin of clypeus feebly convex, bearing 4–6 denticles. Masticatory margin of mandible with a large apical tooth followed by a small subapical tooth, 3–4 denticles and a medium-sized basal tooth; basal margin bearing 2–3 small teeth. Mesosoma relatively slender; promesonotum in profile weakly convex dorsally and sloping gradually to metanotal groove; propodeum with dorsal outline almost straight; propodeal junction roundly angulate; declivity not margined dorsally and laterally. Petiole subsessile, almost as long as high; subpetiolar process well developed and hook-like, its apex directed downward and backward; postpetiole almost as long as petiole, only slightly higher than the latter.

Head including mandible and antennal scape entirely smooth and shiny. Mesosoma extensively smooth and shiny; area of metanotal groove striate; upper portion of metapleuron with about 10 irregular longitudinal rugae. Petiole and postpetiole entirely smooth and shiny. Legs entirely smooth and shiny.

Head and mesosoma dorsally with relatively sparse standing hairs mixed with sparse short hairs over the surface; longest pronotal hair 0.25–0.30 mm long. Body reddish-brown to yellowish-brown; dorsum of head darker. Typhlatta spot located anterior to occipital corner.

Type Material
Holotype worker from S. Thailand, Nakhon Si Thammarat Prov., Khao Nan, rubber tree plantation, 28 IX 2008, W. Jaitrong leg., WJT08-S1101. One hundred and thirty-seven paratype workers, same data as holotype (,, , , , THNHM, UMS).

Etymology
The specific name pertains to the pale body colour.