Small or medium-sized, coarsely hairy, brown or black ants, with monomorphic workers, which have 7-jointed antennae, the funiculus enlarged toward the tip but not clavate and all the joints, except the first, considerably longer than wide. Mandibles moderately large, subtriangular, with coarsely dentate apical border. Clypeus broad and convex. Frontal area indistinct behind. Frontal carinae short, rather far apart, not strongly diverging posteriorly. Eyes not very large, convex, behind the middle of the head; ocelli absent. Thorax with indistinct or obsolete premesonotal suture; mesoepinotal suture deep, the mesoepinotal constriction pronounced; the sides of the mesonotum raised and subauriculate behind. Epinotum armed with a pair of long, acute spines, which are often lobate or expanded at the base; inferior corners of pronotum dentate or spined. Petiole with a long peduncle sharply marked off from the abrupt node, which is high and rounded, subcorneal, sometimes laterally compressed. Postpetiole shaped like the node of the petiole, strongly contracted posteriorly. Gaster subglobose, its basal segment somewhat truncate in front. Legs long; median and hind tibiae with simple spurs; tarsal claws simple.
Female considerably larger than the worker. Head and antennae of very similar structure, the latter being 7-jointed. Thorax robust; mesonotum and scutellum very convex, the pronotum vertical in front though well developed, the epinotum with stouter and broader spines than in the worker. Pedicel as in the worker. Gaster much more voluminous, longer than wide, convex above; the basal segment truncate anteriorly. Wings long, with strongly marked veins, the anterior pair with an open radial cell, a single cubital and a discoidal cell.
Male nearly as large as the female but more slender. Antennae 13-jointed, filiform, the scape short, about as long as the second funicular joint, the first joint very short, not swollen, the remaining joints all much longer than broad. Eyes large but not very convex; ocelli rather small. Mandibles small and vestigial, sublinear, with rounded edentate tips, which do not meet. Frontal carinae short. Mesonotum with Mayrian furrows; epinotum without spines. Petiole very long, its node low; that of the postpetiole of a similar shape, decidedly longer than broad. Gaster cordate, scarcely longer than broad, convex above, concave below. External genital appendages long and narrow, blade-like. Cerci present, but minute. Legs slender. Wings rather short, venation as in the female.
This extraordinary genus may be recognized at once by the 7- jointed antennae of the worker and female and the unique structure of the abdomen in the male. The species are distributed over the Ethiopian, Indomalayan, and Papuan Regions but do not enter Australia (Map 21). The majority of the species and the largest are Ethiopian. The large species form crater nests in the soil; some of the smaller, both in Africa and in the Orient, make small carton nests on the under sides of leaves.
Map 21. Distribution of the genus Myrmicaria .