|Based on Ward et al. (2014) and Blaimer et al. (2018).|
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. (Hita Garcia, Wiesel and Fischer 2013)
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.
|Antennae with 12 segments||Antennae with 11 segments|
|Scapes strongly expanded and incrassate in apical half, with a narrow projecting flange on the leading edge.||Scapes thicker distally but not strongly expanded nor incrassate in apical half, without a projecting flange on the leading edge.|
|Petiole in profile with a long narrow anterior peduncle, without a large anteroventral process.||Petiole in profile with a short and very stout anterior peduncle, with a large anteroventral process.|
|Node of petiole high, not narrowing above.||Node of petiole low, narrower above than below.|
|Anterior subpostpetiolar process a tooth on each side (in all African species).||Anterior subpostpetiolar process a transverse ridge or flange.|
|Gastral tergites 2 to apex not reflexed ventrally.||Gastral tergites 2 to apex relfexed ventrally.|
|Head in dorsal view with frontal carinae strongly expanded, concealing most or allof the scrobal area.||Head in dorsal view with frontal carinae not strongly expanded, most of the scrobal area clearly visible.|
|Body partially or entirely with bizarre pilosity.||All body hairs fine and simple.|
Keys to Species in this Genus
Distribution and Richness based on AntMaps
Known only from the worker caste.
• Antennal segment count 11 • Antennal club 3 • Palp formula 2,2 • Total dental count 7-9 • Spur formula 1 simple, 1 simple; 0, 0 • Sting present
• Antennal segment count 11 • Antennal club gradual • Palp formula 2,2 • Total dental count 6 • Spur formula 1 simple, 1 simple
The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.
- 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.
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.
- Arnold, G. 1917. A monograph of the Formicidae of South Africa. Part III. Myrmicinae. Ann. S. Afr. Mus. 14: 271-402 (page 362, Dicroaspis in Myrmicinae, Meranoplini; Dicroaspis as genus)
- Bolton, B. 1981a. A revision of the ant genera Meranoplus F. Smith, Dicroaspis Emery and Calyptomyrmex Emery (Hymenoptera: Formicidae) in the Ethiopian zoogeographical region. Bull. Br. Mus. (Nat. Hist.) Entomol. 42: 43-81 PDF (page 56, Dicroaspis valid genus, senior synonym of Geognomicus, and revision of genus)
- Bolton, B. 1994. Identification guide to the ant genera of the world. Cambridge, Mass.: Harvard University Press, 222 pp. (page 106, Dicroaspis in Myrmicinae, Stenammini)
- Bolton, B. 2003. Synopsis and Classification of Formicidae. Mem. Am. Entomol. Inst. 71: 370pp (page 203, Dicroaspis as genus)
- Brown, W. L., Jr. 1973b. A comparison of the Hylean and Congo-West African rain forest ant faunas. Pp. 161-185 in: Meggers, B. J., Ayensu, E. S., Duckworth, W. D. (eds.) Tropical forest ecosystems in Africa and South America: a comparative review. Wash (page 180, Dicroaspsis provisional junior synonym of Calyptomyrmex)
- Dlussky, G. M.; Fedoseeva, E. B. 1988. Origin and early stages of evolution in ants. Pp. 70-144 in: Ponomarenko, A. G. (ed.) Cretaceous biocenotic crisis and insect evolution. Moskva: Nauka, 232 pp. (page 80, Dicroaspis in Myrmicinae, Calyptomyrmecini)
- Donisthorpe, H. 1943g. A list of the type-species of the genera and subgenera of the Formicidae. [part]. Ann. Mag. Nat. Hist. 11(10): 617-688 (page 639, Dicroaspis in Myrmicinae, Meranoplini; Dicroaspis subgenus of Calyptomyrmex)
- Emery, C. 1908c. Descriptions d'une genre nouveau et de plusieurs formes nouvelles de fourmis du Congo. Ann. Soc. Entomol. Belg. 52: 184-189 (page 184, Dicroaspis as genus)
- Emery, C. 1915e. Formiche raccolte nell'Eritrea dal Prof. F. Silvestri. Boll. Lab. Zool. Gen. Agrar. R. Sc. Super. Agric. 10: 3-26 (page 15, Dicroaspis subgenus of Calyptomyrmex)
- Emery, C. 1924f . Hymenoptera. Fam. Formicidae. Subfam. Myrmicinae. [concl.]. Genera Insectorum 174C: 207-397 (page 225, Dicroaspis in Myrmicinae, Meranoplini; Dicroaspis subgenus of Calyptomyrmex)
- Forel, A. 1917. Cadre synoptique actuel de la faune universelle des fourmis. Bull. Soc. Vaudoise Sci. Nat. 51: 229-253 (page 244, Dicroaspis in Myrmicinae, Meranoplini; Dicroaspis subgenus of Calyptomyrmex; )
- Wheeler, W. M. 1922i. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. VII. Keys to the genera and subgenera of ants. Bull. Am. Mus. Nat. Hist. 45: 631-710 (page 664, Dicroaspis in Myrmicinae, Meranoplini; Dicroaspis as genus)
- Wheeler, W. M. 1922j. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. VIII. A synonymic list of the ants of the Ethiopian region. Bull. Am. Mus. Nat. Hist. 45: 711-1004 (page 887, Dicroaspis subgenus of Calyptomyrmex)
- Wheeler, W. M. 1934a. Formicidae of the Templeton Crocker Expedition, 1933. Proc. Calif. Acad. Sci. (4) 21: 173-181 (page 176, Dicroaspis in Myrmicinae, Meranoplini)
- Wheeler, W. M. 1935a. Two new genera of myrmicine ants from Papua and the Philippines. Proc. N. Engl. Zool. Club 15: 1-9 (page 7, Dicroaspis revived status as genus; Dicroaspis in Myrmicinae, Meranoplini; Dicroaspis as genus)