Aenictus exilis

Workers were found (in Karema) running in a very diffuse single file over the top of the ground and under leaf litter in a small, recently made clearing at the edge of virgin lowland rain forest. The time was noon of a sunny day (note that 3 colonies of the closely related Aenictus ceylonicus were found foraging in New Guinea between 9 and 11 in sunny mornings, or, in other words, at nearly the same time and under similar condition). The file was very inconspicuous and could not be traced more than a few feet. The Busu River workers were collected in a soil-litter berlesate from the floor of virgin lowland rain forest, in close company with such distinctive Papuan ant species as Dacetinops cibdelus, Strumigenys mayri, Eurhopalothrix biroi, and Eurhopalothrix brevicornis.

Identification
A member of the ceylonicus group.

Key to Aenictus species groups

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

Nomenclature

 *  exilis. Aenictus exilis Wilson, 1964a: 462, fig. 33 (w.) NEW GUINEA.

Worker
Holotype: HW 0.40 mm, HL 0.48 mm, SL 0.31 mm. Antenna 10-segmented. Very similar to workers from sympatric series of ceylonicus (Mayr), differing chiefly in its smaller size, lighter coloration, and weaker sculpturing. (The name exilis means weak or feeble and refers to these characteristics). Mandibles thin and 4-toothed, as in ceylonicus. Cephalic structure as in ceylonicus. Propodeum angulate. Subpetiolar process large, consisting of a forward-directed lobe surmounted by a thin, acutely angulate flange which is directed straight downward. Pilosity moderately abundant; the length of the longest pronotal hairs only about 0.10 mm.

Head shining. Pronotum shining. Propodeal dorsum very weakly microreticulate, feebly shining. Meso-, metapleuron, and sides of propodeum longitudinally rugose, the interspaces weakly microreticulate and subopaque to feebly shining. Dorsa and most of sides of pedicel shining, the remainder weakly microreticulate and subopaque. Concolorus light brownish yellow.

Paratypes: 9 workers from same colony as holotype. Also, 2 workers from lower Busu River, Huon Peninsula, NE New Guinea, 14.V.1955 (Wilson, ace. no. 1052). HW of Karema workers 0.38-0.41 mm, of Busu River workers 0.37, 0.42 mm. The Busu River workers differ from holotype nest series in having propodeal dorsum strongly shining.