Pseudomyrmex goeldii

Ward, Philip S., 2017, A review of the Pseudomyrmex ferrugineus and Pseudomyrmex goeldii species groups: acacia-ants and relatives (Hymenoptera: Formicidae), Zootaxa 4227 (4), pp. 524-542: 533-534

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Pseudomyrmex goeldii


Pseudomyrmex goeldii  group

This is a small but distinctive group, comprising five known species. The distribution of the clade is centered in South America , but two species have penetrated as far north as Nicaragua and Costa Rica, respectively. Unlike most species in the P. ferrugineus  group, the ants of the P. goeldii  group are generalist inhabitants of dead twigs, and they have a timid demeanor. 

Worker diagnosis. Small species (HW 0.47–0.78, HL 0.65–0.93); head longer than broad (CI 0.69–0.85) and eyes strikingly elongate (REL 0.55–0.66). Masticatory margin of mandible with 5–6 teeth; mesial tooth on basal margin about equidistant between apicobasal angle and proximal tooth. Palp formula 5,3 or 4,3. Anterior margin of median clypeal lobe broadly concave, with a weak median protrusion, and with sharp lateral angles. Frontal carinae closely contiguous (FCI 0.010–0.019) and forming a thin anterodorsally elevated ridge, the carinae directed forward onto the median clypeal lobe rather than fusing with the antennal sclerites anterolaterally. Profemur very robust (FI 0.49–0.56). Metanotal groove strongly impressed ( Figs 4–8View FIGURES 4 – 6View FIGURES 7 – 8). Dorsal and declivitous faces of propodeum well differentiated; in profile the juncture between the two varying from weakly to strongly angulate, sometimes producing small, paired tubercles. Petiole relatively short (PL/HL 0.35–0.49), longer than high or wide (PLI 0.51– 0.80, PWI 0.48–0.66), and without a well differentiated anterior peduncle; anteroventral petiolar tooth present. Postpetiole broader than long, with small anteroventral tooth. Body sculpture varying from smooth and shining, with scattered fine punctulae, to densely punctulate-coriarious or coriarious-imbricate. Standing pilosity very sparse (MSC 0–2), a single pair or none at all on dorsum of head, mesosoma (pronotum), petiole and postpetiole; absent from the extensor faces of tibiae (HTC 0, MTC 0). Appressed pubescence moderately dense on petiole, postpetiole and abdominal tergite IV, variably so on rest of body. Color varying from brownish-yellow to dark brown, often bicolored.

Queen diagnosis. Similar to worker except for caste-specific differences. Head more elongate (HL 0.74–0.97, CI 0.62–0.78); median clypeal lobe more protruding; profemur more robust (FI 0.53–0.59); dorsal face of propodeum shorter than declivitous face, the juncture between the two gently rounded, not angulate. Petiole generally more slender than in worker (PL/HL 0.46–0.51, PLI 0.57–0.67, PWI 0.50–0.58). Forewing with 2 submarginal cells, i.e., cross-vein 2rs-m present.

Male diagnosis. Relatively small species (HW 0.53–0.69, HL 0.58–0.74; n = 4). Head longer than broad (CI 0.88–0.92); compound eye large, prominent (REL 0.55–0.60, REL2 0.62–0.65). Mandibles with about 6–8 teeth or denticles on masticatory margin. Palp formula as in females. Surface of median clypeal lobe convex, its anterior margin subtriangular in shape (dorsal view) with sides converging medially to a rounded point. Scape short (SI 0.20–0.23). Petiole and postpetiole slender (PLI 0.54–0.59, PWI 0.41–0.49). Posterolateral corners of sternites IV – VIII not notably protruding ventrally. Posterior margin of subgenital plate (sternite IX) broadly convex, lacking conspicuous posteromedial concavity. Posterior margin of pygidium (tergite VIII) convex, directed posteroventrally. Paramere with angulate or rounded posterodorsal extremity, and a low angulate mediodorsal lobe (as seen in lateral view) representing the summit of a well-developed mesial dorsoventral ridge. Aedeagus with somewhat expanded posterodorsal corner; posterior margin with numerous small teeth (10+), preceded by a sinuous carina on the outer face of the aedeaegus, which converges to the posterior margin dorsally.

Comments. Workers and queens of the Pseudomyrmex goeldii  group are superficially similar to those of the P. pallidus  group (as defined in Ward 1989), with which they share a laterally angulate median clypeal lobe and sparsity of standing pilosity on the body. In the P. pallidus  group, however, the frontal carinae do not form an anterodorsally elevated ridge that is directed forward onto the median clypeal lobe; instead the carinae are directed anterolaterally where they fuse with the antennal sclerites, as in most Pseudomyrmex  . In addition, in the P. pallidus  group the dorsal and declivitous faces of the propodeum usually round into one another, rather than meeting at an angle. The unusual configuration of the frontal carinae in the P. goeldii  group is also seen in the P. subtilissimus  group ( Ward 1989), but in this latter group the median clypeal lobe is laterally rounded, not angulate; the head is distinctly elongate (worker CI 0.56–0.73 versus 0.69–0.85 in the P. goeldii  group); and there is a characteristic pair of setae on the propodeum at the juncture of the dorsal and declivitous faces.