Aenictus philippinensis

Chapman (1963) - "[The workers discovered at 3600 feet] came from a hole in the ground, climbed up a nearby stump, and spent the next hour in which they were observed building a living pyramid in the center of the stump. Some tried to build out from the edge of the stump in a horizontal direction. The next morning I dug around the hole from which they had come, but I found no trace of their bivouac." [Wilson adds.this was on July 29 and 30, 1942, while Dr. Chapman was in the Horns of Negros hiding from the Japanese occupation troops; see his account of this remarkable adventure in the book Escape to the Hills, by James and Ethel Chapman]. Jaitrong & Yamane (2012) - A. philippinensis is very probably restricted to the Philippines and probably sympatric with Aenictus rabori in at least Negros Oriental. We found a colony under a stone near a road.

Identification
A member of the philippinensis species group. A. philippinensis is similar to Aenictus punctatus as they have sculptured head and mandible. However, they differ in some characters. The sculpturing on the head is much weaker in A. philippinensis (superficially reticulate and shiny) than in A. punctatus (finely punctate). Pronotal dorsum is smooth and shiny in A. philippinensis, but finely punctate in A. punctatus. Propodeal declivity is dorsally margined with a low rim in A. philippinensis; the rim is much more developed, in profile distinctly protruding posteriad in A. punctatus.

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

Castes
Known only from the worker caste.



Nomenclature

 * . Aenictus (Aenictus) philippinensis Chapman, 1963: 247, fig. 1 (w.) PHILIPPINES (Negros I.).
 * [Note: fig. 2, not fig. 1 as published.]
 * Status as species: Wilson, 1964a: 473; Bolton, 1995b: 60; Jaitrong & Yamane, 2012: 70 (redescription).

Worker
Wilson (1964) - Syntypes: Worker chosen at random: HW 0.78 mm, HL 0.83 mm, SL 0.61 mm; HW of long series of additional workers, 0.79-0.84 mm. Antenna 10-segmented. Mandibles typical. Clypeus rounded, entire, unarmed. Parafrontal ridge indistinct but 0.28 mm long. Occiput straight, lacking collar. Mesonotum demarcated from mesopleuron by a conspicuous ridge; a striking character shared within the genus only by the Philippine species rabori Chapman. Metanotum strongly impressed. Basal face of propodeum convex. Propodeal junction right-angular. Subpetiolar process a low, inconspicuous, forward-directed lobe. Pilosity less abundant and shorter than in the related pachycerus; length of longest pronotal hairs only 0.25 mm.

Cephalic and mesosomal sculpturing similar to that of pachycerus (q. v.). Postpetiolar dorsum feebly shining; remainder of pedicel microreticulate and opaque. Concolorous medium reddish brown.

Jaitrong & Yamane (2012) - Non-type workers (n = 10): TL 3.70-4.00 mm; HL 0.83-0.88 mm; HW 0.74-0.80 mm; SL 0.55-0.60 mm; ML 1.18-1.25 mm; PL 0.26-0.33 mm; CI 89-91; SI 74-77.

Head in full-face view subretangular, slightly longer than broad, with sides weakly convex and posterior margin almost straight; occipital margin forming a narrow carina; seen in profile occipital corner of head rounded. Antennal scape relatively short, reaching only 2/3 of head length; antennal segment II almost as long as each of III-VI; terminal segment almost as long as VII+VIII+IX. Frontal carinae fused at the level of antennal base to form a single carina and extending beyond the level of the posterior margin of torulus, poorly developed in posterior half. Parafrontal ridge relatively long, extending less than 1/3 of head length, 0.25– 0.28 mm long. Masticatory margin of mandible with a large apical tooth followed by a series of 6–7 denticles of same size. Mesosoma in profile with dorsally convex promesonotum and sloping gradually to metanotal groove; metanotal groove distinct and deep; mesopleuron relatively short, clearly dermacated from metapleuron by a deep groove; propodeum lower than mesonotum, weakly convex dorsally; propodeal junction right-angled; declivity of propodeum shallowly concave, encircled with a distinct rim. Petiole subsessile, slightly longer than high; subpetiolar process very low, its anteroventral corner bluntly angulate; postpetiole slightly longer than petiole and slightly longer than high, with its dorsal outline convex. Legs relatively long with apical halves of femora and tibiae somewhat swollen.

Head superficially reticulate and shiny; mandible very finely striate except along masticatory margin; antennal scape superficially shagreened. Promesonotum finely macroreticulate except dorsal face largely smooth and shiny; mesopleuron, metapleuron, and propodeum densely punctate/reticulate. Both petiole and postpetiole punctate except dorsal face of the latter smooth and shiny. Femora entirely superficially reticulate and shiny, partly smooth and shiny; tibiae weakly punctate.

Head and mesosoma dorsally with relatively sparse standing hairs mixed with short hairs over surface; longest pronotal hair 0.17–0.20 mm long. Entire body reddish brown.

Type Material
Jaitrong & Yamane (2012) - Syntype workers from Philippines, Negros, Horns of Negros, 450 and 1,080 m.

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. 2012. Review of the Southeast Asian species of the Aenictus javanus and Aenictus philippinensis species groups (Hymenoptera, Formicidae, Aenictinae). ZooKeys 193: 49-78.
 * Jaitrong, W., and S. Yamane. "Review of the Southeast Asian species of the Aenictus javanus and Aenictus philippinensis species groups (Hymenoptera, Formicidae, Aenictinae)." ZooKeys 193 (2012): 49-78.
 * Wilson E. O. 1964. The true army ants of the Indo-Australian area (Hymenoptera: Formicidae: Dorylinae). Pacific Insects 6: 427-483.