Onychomyrmex

These uncommon ants have an army-ant life style. They alternate between temporary bivouacs in protected sites on the ground and semi-permanent nests in soil or in rotten logs. Groups of workers forage by forming distinct raiding columns across the surface of the ground. Some species are known to be specialist predators on centipedes. Queens have greatly extended gasters (they are dichthadiiform), and new colonies are formed by the division of established colonies.

Identification
The mandibles are long and slender, with numerous (always more than 3) teeth which vary greatly in size and are scattered along the inner margins, and with a sharp, pointed tooth at their tips which is at least 4 times longer than the next longest tooth. The frontal lobes extend only slightly forward of the antennal sockets and do not cover the clypeus when viewed from the front. The petiole has distinct front and upper faces but lacks a rear face, and its attachment to the gaster is broad and approximately the same height as the petiole so that the upper surfaces of the petiole and gaster are separated by at most a shallow impression. The tibiae of the hind legs usually lack spurs at their tips, but when present they are small, straight and not comb-like (pectinate) (best viewed from the front).

Onychomyrmex workers are most often confused with workers of Amblyopone. However, they differ in having the tooth at the tip of the mandible much longer and in lacking a comb-like spur on the hind tibia.

Species richness
Species richness by country based on regional taxon lists (countries with darker colours are more species-rich). View Data



Nomenclature

 *  ONYCHOMYRMEX [Amblyoponinae]
 * Onychomyrmex Emery, 1895g: 349. Type-species: Onychomyrmex hedleyi, by monotypy.

Wheeler (1916):

Worker
Small, slender, monomorphic. Mandibles rather long, narrow at the base, broadest in the middle, with long, curved, acute tips, their inner borders armed with a number of unequal teeth, some of which, near the middle of the series, are directed backward. Both the maxillary and labial palpi very short, 2-jointed. Clypeus very short, abrupt, with rounded, entire anterior border beset with a regular row of minute teeth. Frontal carinae small, prominent, closely approximated, enlarged and dilated anteriorly, separated by a very narrow groove. Frontal groove lacking. Eyes very small, consisting of about 6 or 8 ommatidia, situated behind the middle of the head. Antennae 12-jointed, funiculus filiform, not clavate or conspicuously enlarged at the tip. Thorax slender, with very distinct promesonotal and mesoepinotal sutures; mesonotum smull, digeoidal, with distinet sutures on all sides. Petiole with a short peduncle in front and a large, prominent compressed ventral projection, the node rounded, scarcely narrowed behind where it articulates by means of its whole posterior surface with the postpetiole. Postpetiole large, convex below, separated by a pronounced constriction from the gaster, which is rather short. Sting very long and well-developed. Legs long; middle and hind tibiae without spurs; terminal joints of the middle and hind tarsi conspicuously elongated and incrassated, with very large, strongly curved, simple claws and large pulvilli.

Queen
Apterous and ergatomorphic. Head broadened in front and more depressed at the anterior corners than in the worker. Eyes very small; ocelli absent. Mandibles more falcate, not abruptly curved at the tips, with only a few short, blunt teeth. Mesonotum somewhat longer than in the worker. Petiole differing from that of the worker in being much broader, with a very short and narrow peduncle and lacking the ventral projection. Constriction between the postpetiole and gaster much less distinct than in the worker. Gaster much larger, elongate elliptical, sting somewhat smaller. In other respects like the worker.

Larva
Slender, smooth and nontuberculate, with twelve very distinct postcephalic segments, the constrictions between which are everywhere deep and conspicuous, even at the posterior end of the body. Head short, rounded, with well-developed, slender, acute, falcate mandibles, destitute of teeth. Clypeus rather long, projecting. Antennae very small. Maxillary sensillae long and prominent. Head sparsely, remainder of body more densely and uniformly covered with short, straight, stiff hairs or bristles.