Aenictus philippinensis

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Aenictus philippinensis
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Dorylinae
Genus: Aenictus
Species: A. philippinensis
Binomial name
Aenictus philippinensis
Chapman, 1963

Aenictus philippinensis casent0249282 p 1 high.jpg

Aenictus philippinensis casent0249282 d 1 high.jpg

Specimen Labels

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.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Indo-Australian Region: Philippines (type locality).

Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Little is known about the biology of Aenictus philippinensis. 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.

Castes

Known only from the worker caste.

Wilson 1964 Army Ant fig 76-83

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • philippinensis. Aenictus (Aenictus) philippinensis Chapman, 1963: 247, fig. 1 (w.) PHILIPPINES. See also: Wilson, 1964a: 473; Jaitrong & Yamane, 2012: 70.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Description

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 (Museum of Comparative Zoology).

References