Pseudomyrmex cognatus

Pseudomyrmex cognatus ranges from Chiapas, Mexico to Nicaragua, and has been recorded from mixed tropical/temperate mesic forest, montane rainforest, montane rainforest edge, oak-pine forest, mixed pine-mesophyll forest, oak cloud forest, roadside, and old field/pasture, at elevations ranging from 1,105 m to 2,000 m (mean 1,507 m; n  =  47). Nests have been collected from dead twigs of various woody plants, including Asteraceae, Fabaceae, Orchidaceae, and Pinus; one was collected from a dead sedge culm.

Identification
Medium-sized species (HW 0.93–1.06) with moderately elongate head (CI 0.82–0.88) (Fig. 7) and relatively large eyes (see REL and REL2 values); frontal carinae separated by less than basal scape width; metanotal groove weakly impressed, in profile barely discernable; dorsal face of propodeum flat and more or less differentiated from declivitous face, rounding into the latter, and the two faces subequal in length; petiole moderately slender (PLI 0.49–0.57, PL/HL 0.53–0.59); in profile petiole with slight or no anterior peduncle, the anterodorsal face flat to convex, ascending gradually to summit in posterior half of node, then rounding into more steeply descending posterior face; profemur slender; hind leg relatively short (LHT/HL 0.71–0.77). Head subopaque, densely punctulate-coriarious, the punctulae on vertex usually separated by less than their diameters. Standing pilosity sparse, absent from propodeum and mesonotum (MSC 2–5). Head, postpetiole, gaster and legs dark brown, mesosoma and petiole varying from concolorous to lighter medium-brown, not strongly contrasting, however, with rest of body (mesosoma sometimes darkened dorsally); mandibles, antennae, and distal portions of legs tending to be a lighter medium-brown to yellowish-brown.

This is a widespread and rather common Mesoamerican species that was previously confused with Pseudomyrmex championi, although the two are not sister taxa—in fact, UCE data demonstrate that they belong to different complexes within the P. elongatulus group (Fig. 1). Pseudomyrmex cognatus can be recognized by the combination of dark brown coloration of most of the body (mesosoma often lighter but not contrastingly so); densely punctulate-coriarious head; relatively large eyes (worker REL 0.45–0.48, queen REL 0.42–0.46); and weakly developed metanotal groove (in the worker). For distinctions between P. cognatus and P. championi, see under the latter species.

Workers from a single nest collection from Parque Florencia, Sacatepéquez, Guatemala (PSW15039) have more widely separated frontal carinae (MFC 0.065–0.070; n = 3), shorter eyes (REL 0.43–0.45), and a broader and shorter petiole (PWI 0.56–0.58, PL/HL 0.50–0.53). In the UCE phylogeny this sample is sister to all others of P. cognatus (Fig. 1). We have no other P. cognatus workers from this site, i.e., no sympatric association with more ‘typical’ P. cognatus that would confirm PSW15039 as a distinct species. Hence there is some ambiguity about the status of these divergent individuals. For the moment we treat them as conspecific with P. cognatus, while noting that further study might support their treatment as a different species.

Distribution based on Regional Taxon Lists
Neotropical Region: El Salvador, Guatemala, Honduras, Mexico, Nicaragua.

Nomenclature

 * . Pseudomyrmex cognatus Ward & Branstetter, 2022: 20, figs. 7, 8, 22 (w.dq.) MEXICO (Chiapas).

Type Material

 * Holotype Worker. MEXICO Chiapas: Tziscao, Lagos de Montebello, 1,500 m, 16° 05′ N 91° 41′ W, 21 Dec 1991, ex dead twig of vine, mixed tropical/temperate mesic forest, P.  S. Ward PSW11560 (UNAM) (CASENT0863537).
 * Paratypes: series of workers, 1 dealate queen, same data as holotype (CASC, CZUG, IEXA, JTLC, MCZC, PSWC, UCDC, USNM).