Pseudomyrmex micans Ward

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 : 536-538

Pseudomyrmex micans Ward , sp. nov.

( Fig. 6 )

Pseudomyrmex goeldii ; Chomicki et al. (2015: 4) (misidentification).

Type material. Holotype worker. PERU San Martín: Tarapoto , 350 m, 6°29ʹS, 76°22ʹW, 25 Aug 1986, ex dead twig, edge of second-growth rainforest, P. S. Ward PSW08734 ( MZSP) (CASENT0794101) . Paratypes. Series of workers, 1 male, same data as holotype ( CASC, JTLC, MCZC, PSWC, UCDC, USNM).

Other material examined ( PSWC). BOLIVIA Santa Cruz: 11 km NE Aserradero Moira , 180 m (P. S. Ward).

Worker measurements (n = 6). HL 0.67–0.74, HW 0.52–0.55, MFC 0.007–0.009, LHT 0.39–0.42, CI 0.74– 0.80, REL 0.59–0.61, REL2 0.75–0.80, FCI 0.013–0.016, FI 0.53–0.55, PLI 0.64–0.69, PWI 0.56–0.63.

Worker diagnosis. Small species (HL 0.67–0.74, HW 0.52–0.55) with elongate head and eyes (CI 0.74–0.80, REL 0.59–0.61, REL2 0.75–0.80); masticatory margin of mandible with 5 teeth; palp formula 4,3; juncture between dorsal and declivitous faces of propodeum only weakly angulate, not producing lateral tubercles; anterodorsal face of petiole ascending gently ( Fig. 6 b). Head smooth and shiny with scattered fine punctulae; pronotum similar, remainder of mesosoma becoming sublucid, with coriarious-imbricate sculpture on most surfaces, but with shining areas on the mesopleuron and metapleuron; petiole, postpetiole and gaster with moderately dense pubescence. Standing pilosity sparse (MSC 2); paired erect setae present on pronotal humeri, petiole and postpetiole. Dark brown, mandibles, frontoclypeal complex and tarsi lighter; pronotum, petiole and postpetiole sometimes a lighter medium- to yellowish-brown.

Comments. Based on the weakly angulate propodeum this species was initially considered conspecific with P. goeldii (and called this in Chomicki et al. 2015), but a more careful examination of relevant material reveals substantial differences: P. micans is smaller in size (HW 0.52–0.55 versus HW 0.65–0.66 in the three syntype workers of goeldii ), and has more elongate eyes (REL 0.59–0.61 versus 0.55–0.56), a shorter petiole (PLI 0.64– 0.69 versus 0.51–0.59), and a more shiny mesosoma. P. micans appears to be closely related to P. laevifrons , differing primarily by the less pronounced angular juncture of the dorsal and declivitous faces of the propodeum; by the weaker body sculpture, especially on the metapleuron, which is more strongly shining; by slightly lower REL2 values (see above); and by the shape of the petiole, which is lower, wider, and with a more gently sloping anterodorsal face (compare Figs 5 b and 6b). Collections from Peru and Bolivia can be separated into one or the other of these two forms, based on the features listed above. This includes diagnostic differences in petiolar metrics: PLI 0.72–0.80 in P. laevifrons (n = 5) versus 0.64–0.69 in P. micans ; DPW/ PH 0.76–0.85 in P. laevifrons versus 0.88–0.92 in P. micans . In other parts of the range of P. laevifrons , where P. micans is apparently absent, the petiolar diagnostics break down, and some workers show a weakening of the pronounced angle at the juncture of the dorsal and declivitous faces of the propodeum. One interpretation of this pattern is that P. laevifrons ranges from Central America to Bolivia and central Brazil, undergoing character displacement where it overlaps with the more southern species, P. micans . An alternative hypothesis is that the species are distinct in some areas but that differences are obscured by gene flow elsewhere. The entire complex of populations would benefit from a focused phylogenetic analysis.

Distribution and biology. As currently conceived P. micans is known only from rainforest sites in Peru (nest ex dead twig, edge of second-growth rainforest) and Bolivia (workers foraging on recent Tabebuia and Hymenaea treefalls).

Figures

FIGURES 4 – 6. Pseudomyrmex goeldii group, workers, full-face dorsal view of head (a) and lateral profile of body (b). 4, P. goeldii, Brazil (CASENT 0907543); 5, P. laevifrons, Bolivia (CASENT 0762973); 6, P. micans, Peru (CASENT 0794101). Images from AntWeb (www. antweb. org); photographers Will Ericson (4) and Matthew Prebus (5, 6).