Megalomyrmex incisus Smith

Longino, John T., 2010, A taxonomic review of the ant genus Megalomyrmex Forel (Hymenoptera: Formicidae) in Central America, Zootaxa 2720, pp. 35-58 : 45-46

Megalomyrmex incisus Smith

( Figs 1 D, 4A)

Megalomyrmex incisus Smith, M.R. 1947: 102 . Holotype worker: Barro Colorado Island, Panama, Jul–Oct 1943 (Zetek) [USNM] (not examined). Brandão, 1990: 451, description of male. Brandão, 2003: 157 , description of queen.

Measurements. Worker: HW 0.65–0.87, HL 0.63–0.86, SL 0.63–0.78, ML 0.98–1.18 (n=20, from Brandão, 1990). Geographic range. Southern Mexico south to central Brazil and Peru, absent in Costa Rica.

Biology. This species occurs in moist to wet forest habitats, from sea level to 1000 m elevation. It is most often encountered as workers in Winkler samples of sifted leaf litter. Colonies have twice been collected from dead wood on the forest floor ( Brandão, 2003).

Comments. Material from Central America and Venezuela is very similar in color and mandibular dentition. Workers are solid black, and the basal teeth of the mandible vary in size, the second from the base being much larger than the flanking teeth. As a result the mandible appears falcate rather than triangular. A collection from Colombia is distinctive, with the color lighter red brown and the basal teeth of the mandible of more uniform size. Other size and shape characters, including the highly distinctive petiole, are the same as other M. incisus . M. incisus has a range disjunction. It is moderately abundant in Winkler samples from Guatemala and southern Mexico, occurs in Panama and Venezuela, yet has never been collected in Costa Rica, in spite of extensive survey work there.

Material examined. BRAZIL: Amazonas: Manaus, 03°07'S, 060°02'W, 3 Nov 1993 (A. B. Casimiro); COLOMBIA: Leticia: El Zafie, 04°13'S, 069°56'W, 150 m, 2–4 Oct 2007 (L. E. Franco & S. Florica); GUATEMALA: Izabal: 5 km NW Morales, 15°30'38"N, 088°51'39"W, 195 m, 2º lowland tropical rainforest, 17 May 2009 ( LLAMA); 16 km ESE Morales, 15°24'40"N, 088°42'43"W, 440 m, 19 May 2009 ( LLAMA); Petén: 13 km NW Machaquilá, 16°26'44"N, 089°33'00"W, 400 m, tropical moist forest, 27 May 2009 ( LLAMA); MEXICO: Chiapas: 8.8 km SE Salto de Agua, 17°30'48"N, 092°17'43"W, 50 m, mixed secondary rainforest, 14 Jul 2007 (R. S. Anderson); Playón de la Gloria, 16°08'52"N, 090°53'48"W, 170 m, 24 Jun 2008 ( LLAMA); Lago Metzabok, 17°07'32"N, 091°37'51"W, 570 m, lowland wet forest, 6 Jun 2008 ( LLAMA); Nahá, 16°58'49"N, 091°35'10"W, 860 m, 2º mesophil forest, 12 Jun 2008 (M. Branstetter); PANAMA: Canal Zone: Barro Colorado Island, 09°09'N, 079°51'W, 100 m, 2 Jul 1979 (W. L. Brown); PERU: Pasco: nr. Pozuzo, 1000 m, steep primary forest above farms, 4–6 Jun 1981 (C. Kugler & R. R. Lambert); VENEZUELA: Aragua: 1.6 km SSW Cumboto, 10°23'19"N, 067°47'52"W, 150 m, riparian dry forest, 15 Aug 2008 (J. Longino).

Figures

FIGURE 1. Variation in mandibular dentition among (A) foreli, (B) symmetochus, (C) drifti, (D) incisus, (E) mondaboroides, and (F) silvestrii.