Oligomyrmex (Aeromyrma) petulcus (Wheeler)

Major - Type location Zaïre (Aëromyrma petulca, Wheeler, 1922: 166, illustrated; in Oligomyrmex by Ettershank, 1966: 124) from Malela, collector Lang & Chapin; major only described. Known from a single specimen .

Wheeler's (1922) description is -

MAJOR - Length 2.5 mm. Head suboblong, nearly one and one-half times as long as broad, with feebly convex sides and rather deeply and angularly excised posterior border. Anterior ocellus well developed; eyes very small, consisting of about six ommatidia, situated at the anterior third of the head. Posterior corners of the latter with a low but distinct ridge produced on each side into a minute tooth. Mandibles convex, with 4 small, subequal, rather acute apical teeth, and a large blunt and flattened basal tooth. Clypeus flat, ecarinate, its anterior border feebly and sinuately excised in the middle, its posterior portion narrow, rectangular, extending back between the diverging frontal carinae. Frontal groove distinct. Antennae 10-jointed; scapes rather slender and curved at the base, reaching to the middle of the sides of the head; joints 2 to 7 of the funiculus minute, subequal, nearly as broad as long (somewhat too long in the figure); club a little shorter than the remainder of the funiculus, with the basal joint longer than broad and about one-third as long as the terminal joint. Thorax decidedly shorter and narrower than the head; pro- and mesonotum convex, steep in front, rounded above; promesonotal suture distinct; mesonotum subcircular; metanotal sclerite distinct. In profile the dorsal outline of the mesonotum slopes backward continuously with the base of the propodeum without a distinct impression at the metnotal groove. Propodeum with a small tooth on each side, its declivity longer than its base, rather steeply sloping. Petiolar node compressed anteroposteriorly, in profile with a rather angular summit, from above transverse; postpetiole transversely elliptical and somewhat broader than the petiole, with a blunt ventral tooth. Gaster voluminous, distended with a transparent liquid, elongate elliptical, longer than the remainder of the body, its anterior border straight in the middle. Legs short.
Subopaque; mandibles, posterior portion of clypeus, frontal area, mesonotum, and gaster shining; mandibles sparsely and indistinctly punctate; head finely and regularly longitudinally rugulose; sparsely and rather coarsely punctate posteriorly; gaster with fine, scattered, piligerous punctures. Hairs yellowish, moderately abundant, suberect, of uneven length, most conspicuous on the dorsal surface; very short, dense and appressed on the appendages. Ferruginous red; legs and antennae paler and more yellowish; gaster dark brown above, with the venter and bases and apical borders of the segments broadly yellowish.
Described from a single specimen taken by Lang and Chapin at Malela "from a small mushroom-shaped termitarium," probably belonging to a colony of Eutermes fungifaber Sjöstedt.

A. petulca differs from africanus Forel from the Kalahari [Botswana] in its slightly smaller size, darker color, in having the postpetiole only slightly broader than the petiole (nearly twice as broad in africanus), in possessing propodeal teeth and longitudinal rugae on the head. In africanus, the head is finely reticulate and the remainder of the body is evidently more shining than in petulcus. In nossindambo [from Magagascar] the head is broader and less sharply rugulose, the thorax is more deeply impressed at the metanotal groove suture, the antennal scapes are much shorter, the anterior ocellus is smaller and the color is paler.
Forel states that the gaster of the africanus soldier is "transparent yellow," which indicates that it was full of a clear liquid as in petulcus. This condition is seen also in the soldiers of many species of Pheidole in Australia and in our Southern States and seems to indicate that this caste in the two genera mentioned often functions as replete or food- storage individuals as in the honey ants (Myrmecocystus, Leptomyrmex, Melophorus, Plagiolepis, and Prenolepis).

NOTE: This specimen from the holotype images (see below) is a queen.  The wing attachments are clear and the central ocellus on the head appears not to occur in major workers of the genus.

The photomontage is collated from the AMNH Congo Expedition website. The photographs of the holotype specimen (labelled as Aeromyrma petulca) were taken by Brian Fisher as part of the VCA project at the California Academy of Sciences - http://www.antweb.org/specimen.do?name=casent0003148.