Dicroaspis

An endemic Afrotropical genus with just two named species, Bolton (1981b) suggested that even these might be variations of the same form. The biology of this genus remains to a great extent unknown, although collection data suggests that these ants live in the leaf litter of rainforests. (Garcia, Wiesel and Fischer 2013)

Identification
Bolton (1981) - When Emery (1908) first described Dicroaspis he treated it as a good genus, closely related to Calyptomyrmex but separated from it by a reduced antennomere count, the shape of the head and the presence of simple, as opposed to bizarre, pilosity.

Between 1908 and 1915 a few Calyptomyrmex species were described as having 11 antennal segments rather than 12. The present study has shown that those Calyptomyrmex species for which an 11-merous count was claimed, and which were consequently placed in subgenus Dicroaspis (arnoldi, clavisetus, foreli, pusillus) were all based on miscounts of the narrow annular segments of the antennae; in fact all of these species, and all known Calyptomyrmex species to date, have 12-segmented antennae.

Characters separating Calyptomyrmex and Dicroaspis are as follows; the first three characters and the final one are the most important.

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



Nomenclature

 *  DICROASPIS [Myrmicinae: Stenammini]
 * Dicroaspis Emery, 1908b: 184. Type-species: Dicroaspis cryptocera, by monotypy.
 * Dicroaspis subgenus of Calyptomyrmex: Emery, 1915g: 15; Forel, 1917: 244; Wheeler, W.M. 1922a: 664, 887; Emery, 1924d: 225.
 * Dicroaspis as genus: Arnold, 1917: 362; Wheeler, W.M. 1935a: 7 (in key).
 * Dicroaspis senior synonym of Geognomicus: Bolton, 1981a: 56.
 * GEOGNOMICUS [junior synonym of Dicroaspis]
 * Geognomicus Menozzi, 1924b: 220. Type-species: Geognomicus wheeleri (junior synonym of Dicroaspis cryptocera), by original designation.
 * [Geognomicus as genus: Wheeler, G.C. & Wheeler, J. 1985: 257 (anachronism); Dlussky & Fedoseeva, 1988: 81 (anachronism).]
 * Geognomicus junior synonym of Dicroaspis: Bolton, 1981a: 56; Bolton, 1994: 106.

Worker
Bolton (1981) - Myrrnicine ants with triangular mandibles whose apical (masticatory) margins are armed with 7-8 small, spaced-out teeth. Palp formula 2,2 based on an in situ count. (Maxillary palp apparently has a large basal and much smaller apical palpomere; the labial palp has two conspicuous large segments.) Clypeus with a narrow anterior apron which overhangs the basal margins of the mandibles. Median portion of clypeus behind the anterior margin vertical or nearly so, terminating above in a projecting biramous appendage or fork; this clypeal fork almost on a level with the frontal lobes and projecting out over the basal portions of the mandibles. Frontal lobes strongly expanded and overhanging the anterior clypeal apron. Posteriormost part of the clypeus, behind the clypeal fork, very narrow and deeply inserted between the frontal lobes. Antennae with II segments, the 3 apical flagellomeres forming a strong club. Scapes not strongly incrassate in their distal halves. Antennal scrobes present, extensive and deep, running back well beyond the level of the eye, bounded above by the posteriorly-divergent frontal carinae and below by a ridge running above the eye. Frontal carinae not strongly expanded laterally over the scrobes so that most of the scrobal concavity is clearly visible in dorsal view. Promesonotum forming a single convexity in profile. Propodeum sloping steeply, armed with a pair of short, stout spines. Metapleural lobes rounded. Petiole with a short, very thick and dorsally very broad anterior peduncle, with a ventral process present anteriorly. Petiole node low and rounded, tapering dorsally from a broad base. Postpetiole with an anterior process ventrally which appears as a broad tooth in profile but which is seen to be a broad transverse flange or lip in anterior view, running the width of the segment. First gastral tergite large, projecting much further than the first stemite and weakly vaulted apically so that the remaining tergites are reflexed and the sting orifice is ventrally situated. Pilosity dense, the hairs simple and fine; without bizarre pilosity.