Gnamptogenys triangularis is a relatively large, black ant with more reddish legs that is characterized by deep longitudinal grooves and ridges that the run the lengths of the head, mesosoma and gaster. Little is known about the ecology of the ant, other than that it is believed to be a millipede specialist and is associated with humid forests and arboreal foraging (Costello et al., 2003; Deyrup et al., 2000; Lattke et al., 2004; Longino, 2012). Gnamptogenys triangularis is native to the Neotropics, where it ranges from Costa Rica to Argentina (Lattke et al., 2007), and is introduced in Florida (Deyrup, 2003; Deyrup et al., 2000; Deyrup et al., 1989), Alabama (MacGown & Forster, 2005), and Mississippi (MacGown, 2012). The earliest known specimens from Florida (first reported as G. aculeaticoxae (Santschi)) date to 1985, and it is so rare there that it is believed to have negligible effects on the native fauna (Deyrup et al., 2000).
Diagnosis of worker among Antkey species. Antenna 12-segmented. Antennal insertions at least partly covered by frontal lobes. Anterior margin of clypeus not denticulate. Eyes medium to large (greater than 6 facets); situated at or above midline of head. Mandibles triangular. Metanotum does not form a prominent convexity bordered by distinct suture lines. Propodeum armed with small teeth or denticles. Waist 1-segmented. Petiole narrowly attached to gaster; has conspicuous posterior face. Petiolar node relatively quadrate and subpetiolar process broad in profile with a blunt anterior angle and an acute posterior angle. Subpetiolar process narrow with a blunt posterior angle and lacking a distinct anterior angle. Abdominal segment 4 with deep longitudinal furrows; distinct constriction between abdominal segments 3+4. Gaster armed with sting. Tarsal claws with subapical tooth. Hind coxae armed with dorsal spine.
Gnamptogenys triangularis, and its geographic and morphological variation, is treated in the taxonomic works of Brown (1958)and Lattke (2004; Lattke et al., 2007). In particular it should be noted that the propodeal teeth vary in size from small denticles to well-formed teeth. The only other species of Gnamptogenys in North America is G. hartmani (Wheeler, W.M.), from which Gnamptogenys triangularis can be separated by its much larger size, shorter erect hairs, and the presence of propodeal teeth. Among other introduced ants, Gnamptogenys triangularis might be most confused with ponerine genera, but can be separated by the eyes which are above the midline of the head, the distinct sulcate sculpture, the coxal tooth, and the deep constriction between abdominal segments 3+4. Among commonly intercepted ants, Gnamptogenys triangularis is most likely confused with Ectatomma species, but can be separated by the lack of convexity and suture lines of the mesonotum, the presence of the coxal spines, and the sulcate sculpture.
Native range. Neotropics: Costa Rica to Argentina.
Introduced range. USA: Alabama, Florida, Mississippi.