Pseudomyrmex elongatulus (Dalle Torre, 1892)

Ward, Philip S. & Branstetter, Michael G., 2022, Species Paraphyly and Social Parasitism: Phylogenomics, Morphology, and Geography Clarify the Evolution of the Pseudomyrmex elongatulus Group (Hymenoptera:, Insect Systematics and Diversity 6 (1), pp. 1-31 : 9

Pseudomyrmex elongatulus Group

Worker Diagnosis. Moderate in size (HW 0.82–1.21, LHT 0.68– 1.12), with a variably elongate head (CI 0.67–0.96), and medium to large eyes (REL 0.38–0.59, REL2 0.46–0.66). Masticatory margin of mandible with 5–6 teeth; mesial tooth on basal margin closer to apicobasal angle than to proximal tooth. Palp formula 6,4. Median clypeal lobe laterally rounded. Frontal carinae separated by basal scape width or less (FCI 0.02–0.07). Profemur relatively slender in most species (FI 0.37–0.49). Pronotal humeri and lateral margins of pronotum rounded. Metanotal groove varying from moderately impressed to absent. Basal and declivitous faces of propodeum weakly to moderately differentiated and usually subequal in length, in profile the juncture between the two gently rounded. Petiole relatively long and slender (PL/HL 0.48–0.69; EL/PL 0.72–0.90), much longer than high or wide (PLI 0.43–0.61, PWI 0.41–0.58); petiole with small anteroventral tooth; anterior peduncle of petiole weakly to moderately differentiated. Postpetiole broader than long, with small anteroventral tooth. Body sculpture punctulate-coriarious to coriarious-imbricate, the integument sublucid to opaque; dorsum of head never with extensive smooth, shiny interspaces; punctulae usually separated by their diameters or less. Standing pilosity generally sparse, nearly always absent from the extensor faces of tibiae, and usually present as 1–2 pairs on the pronotum, petiole, and postpetiole, while being absent from mesonotum and propodeum (MSC 2–8); one exceptional species with greater amounts of pilosity (MSC 23–28, HTC 0, MTC 1–2) including on the mesonotum and propodeum. Appressed pubescence dense but short on most of body, including head and abdominal tergite IV. Color varying from light yellow- or orange-brown to dark brownish-black, often variously bicolored.

Comments. In an earlier synopsis of Pseudomyrmex species groups ( Ward 1989), the P. elongatulus group was subsumed under the P. pallens group. The two groups share a number of similar worker characteristics (6,4 palp formula, 5–6 teeth on the masticatory margin of the mandibles, and laterally rounded median clypeal lobe) but molecular studies have demonstrated that they are not closely related ( Ward and Downie 2005, Chomicki et al. 2015). A recent worker-based key to Pseudomyrmex species groups ( Ward 2017) separated the P.elongatulus group and P. pallens group primarily by geography: the species in the P. pallens group are almost wholly confined to South America, with just one species, P. pallens , extending north of Colombia as far as Costa Rica, while the P. elongatulus group occurs from southwestern United States to Costa Rica.Workers of the one overlapping species, P. pallens , can be distinguished from those of the P. elongatulus group by the combination of dense standing pilosity (MSC 13–28) and long eyes relative to petiole length (EL/PL 0.91–1.20).