Megalomyrmex drifti

Boudinot et al. (2013) - Megalomyrmex drifti is a small leaf-litter nesting species which have been collected in twigs and leaves (Longino 2010; T. McGlynn pers. comm.) as well as in many leaf litter sifting collections (Brandão 1990; Kempf 1970; Longino 2010; herein). These observations, although attributed to M. drifti, likely apply to or are of other species in the drifti complex.

Identification
Boudinot et al. (2013) - Uniquely identified among Central American Megalomyrmex by the following combination: (1) basal and masticatory margins indistinct; (2) small (ML < 1.0 mm); (3) disc of katepisternum smooth and shining; (4) occipital carina obscured by vertex in full-face view; (5) eye normally-developed and relatively close to lateral clypeal margin (EL > 0.10 mm, OMI < 60); (6) scape relatively short (SI < 85). Queen Similarly identifiable as worker, alate.

Distribution
Megalomyrmex drifti, as now delimited, is known in Central America from sea-level to mid-elevation (750 m) wet forests.

Distribution based on Regional Taxon Lists
Neotropical Region: Argentina, Brazil, Colombia, Costa Rica, Ecuador, French Guiana, Guatemala, Guyana, Honduras, Mexico, Nicaragua, Panama, Paraguay, Peru, Suriname, Trinidad and Tobago, Venezuela.

Biology
This species occurs in moist to wet forest habitats, in mature and second growth forest. Most collections are from below 600 m elevation, but collections from 1500 m cloud forest are known. Workers and occasionally queens are moderately abundant in Winkler samples of sifted litter. In Costa Rican wet forest I found a nest in a dead stick in the leaf litter; it contained abundant workers, brood, alate queens, and males. The collection was made on 9 November 2002, the height of the wet season.

Nomenclature

 *  drifti. Megalomyrmex drifti Kempf, 1961b: 504, figs. 9-11 (w.q.) SURINAM. Brandão, 1990: 448 (m.). See also: Kempf, 1970b: 362.

Boudinot et al. (2013) - Kempf (1970) stated that Megalomyrmex drifti displayed a strong morphocline across South America; Brandão (1990) and later Longino (2010) concurred. From the Central American material available to us, we found morphological, geographic, and genetic (unpubl. data) evidence for three new species previously attributed to M. drifti. Our newly restricted M. drifti is found in sympatry with two new drifti complex species, Megalomyrmex megadrifti and Megalomyrmex osadrifti. Although only collected in parapatry with M. drifti, Megalomyrmex brandaoi is remarkably distinct. Previously, Brandão (1990) suggested that the observed morphocline could be caused by high population viscosity due to the production of ergatoid gynes; to our knowledge, ergatoid queens have only been reported from an unknown drifti complex species from Rio Palenque, Ecuador, and Bocaiuva, PR, Brazil (Brandão 1990). It remains to be determined how many drifti  complex species are present in South America. As well, the male of M. drifti has previously been described (Brandão 1990); it is not known to which drifti complex species these described males belong.

Worker
Boudinot et al. (2013) - (holotype, from Brandão 1990): HW 0.45, HL 0.60, SL 0.38, ML 0.60, CI 75, SI 63. (Kempf 1961: HL 0.51, SL 0.37, EL 0.11, ML 0.61, SI 73.) workers(n=9): HW 0.43–0.48, HL 0.52–0.56, SL 0.41–0.45, OMD 0.06–0.08, EL 0.12–0.15, ML 0.63–0.72, CI 84–88, SI 78–82, EI 29–32, OMI 43–57.

Head Palpal formula 3,2. Basal and masticatory margins of mandible indistinct, curving evenly from basal to masticatory margin. Mandible with 4–7 teeth; apical two teeth largest; apical tooth slightly less than twice as long as subapical; 2–5 very small basal teeth. Dorsal surface of mandible smooth and shining, interrupted by weak piligerous punctae. Clypeus truncate in profile view, with median seta often raised on a small tubercle. Clypeal carinae present, distinct to weak; diverging anteriorly. Clypeus, between antennal insertions, narrower than maximum diameter of scape. Antennal fossa encircled by 2–4 complete carinulae. Malar area roughened in anterior half, smooth posteriorly. Compound eye with about 2–7 ocular setae. Compound eye relatively close to lateral clypeal margin (OMI < 60). Scape relatively short (SI < 85). Occipital carina short, distinct; obscured by vertex in full-face view; extending anteroventrally less than one eighth length of postgenal bridge. Mesosoma Katepisternum and promesonotum smooth and shining, propodeum smooth and shining except for 4 close-set metapleural carinulae. Metapleural carinulae not reaching meso-metapleural suture. Metanotal depression a deep incision. Propodeum with dorsal and posterior faces meeting at a bluntly rounded, raised angle; propodeum dorsolaterally marginate; dorsal margin concave in profile view. Propodeal foramen complete to weak dorsomedially. Meso- and metabasitarsi tubular. Metasoma Petiole and postpetiole predominantly smooth and shining, except for occasional weak roughness posteroventrally on the petiole, and concentric girdling carinulae on posterior bases of petiole and postpetiole. Posterior petiolar base distinct from posterodorsal petiolar face. Subpetiolar process a small, distinct, posteriorly-pointed denticle. Postpetiolar sternum weakly bidentate anteriorly. Lancets of sting apparatus flattened, about three times as thick as metasomal seta. Setation Fine; head dorsum with somewhat dense medium to long subdecumbent to erect setae, in addition to somewhat denser short appressed to subdecumbent setae; scape with appressed setae, sometimes with decumbent to subdecumbent setae; promesonotum with about 11–12 setae on each lateral half, about 3–5 longest setae; first gastric tergum with somewhat more dilute long suberect setae, and with at least 10, but more often greater than 20 short appressed setae. Head, meso- and metasoma shining black to dark brown, sometimes pale brown; legs, antennae, and mandibles yellow-brown.

Queen
Boudinot et al. (2013) - (n=2): HW 0.53–0.55, HL 0.60–0.61, SL 0.48, OMD 0.07, EL 0.19, ML 0.87, CI 89–90, SI 80–81, EI 35–36, OMI 37–38.

Similar to worker, but with alate-condition mesosoma, coarser sculpturation, and more mesosomal setation. Wing venation not observed.

Type Material
Holotype worker, paratype workers, queen: SURINAM, Dirkshoop (examined).

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