Nesomyrmex vargasi Longino, 2006

Arredondo, Brandon S. & Guerrero, Roberto J., 2025, The ant genus Nesomyrmex Wheeler (Formicidae, Myrmicinae) from the threatened Colombian tropical dry forest: three new species, a new synonymy, and new distributional data, ZooKeys 1232, pp. 131-172 : 131-172

Nesomyrmex vargasi Longino, 2006

Figs 27 , 29

Nesomyrmex vargasi Longino, 2006: 136. Holotype worker: Costa Rica, Heredia Prov. [ INBC]. (AntWeb image examined, JTLC 000008517, JTLC 000008518, LACMENT 144699).

Worker measurements.

(n = 5) HL 0.70–0.76, HW 0.64–0.68, SL 0.54–0.61, ML 0.28–0.33, EL 0.15–0.16, PW 0.42–0.46, PTW 0.14–0.18, PPW 0.25–0.27, WL 0.88–0.96, PH 0.24–0.30, PTL 0.33–0.38, PTH 0.19–0.21, PPL 0.18–21, PPH 0.21–0.23, GL 0.79–0.91. CI 89–91, SI 84–89.

Geographic range.

Colombia, Costa Rica.

Examined material.

Colombia • 1 worker; Bolivar, Zambrano ; 9.744721°N, 74.82421°W; 1993–1994; Pitfall; IAvH -E-251258 • 1 worker; Cesar, Valledupar, Vda. Tierras nuevas ; 10.241965°N, 73.761216°W; 881 m a. s. l.; 31 Mar. 2016; R. Achury leg.; Pitfall; CBUMAG:ENT:41665 . • 1 worker; Vichada, Cumaribo, Cgto. Santa Rita, Parque Nacional Natural el Tuparro ; 5.331667°N, 67.890833°W; 135 m a. s. l.; 08–10 Feb. 2004; I. Quintero; E. González legs.; Winkler; IAvH -E-79867 .

Note.

Longino (2006) presents the diagnosis for N. vargasi but does not fully describe the species. To address the possible variability of this taxon, we offer a redescription of the worker caste based on specimens from Colombia.

Diagnosis.

Anterior margin of pronotum convex; mesosoma with marked longitudinal striations, space between the striae smooth and shiny; dorsum of postpetiole smooth and shiny; clypeus smooth and shiny; body surface smooth and shiny; antennal scape and legs with erect hairs ( Longino, 2006).

Description.

Worker. In full-face view, head subquadrate, slightly longer than wide (CI: 89), slightly narrowing behind the eyes; occipital margin slightly straight; occipital angles rounded; lateral margins slightly convex, converging posteriorly; anterior margin of clypeus rounded, projecting over mandibles; mandible triangular; inner margin with five teeth, separated from basal margin by fifth tooth; lateral eyes, with 12 ommatidia at greatest diameter, situated toward mid-length of head; frontal lobes slightly expanded, antennal insertions partly exposed; front carina extending to anterior margin of eye; antenna with 11 antennomeres; scapes of moderate size (SI: 84), at rest reaching occipital margin; pedicel longer than wide, as long as next two antennomeres; antennal club with three antennomeres.

Mesosoma. In lateral view, mesosomal profile convex; in dorsal view, pronotum wider than long, with its greatest width towards anterior margin, anterior margin of pronotum slightly convex; humeral angles slightly angulated; lateral margins of pronotum curved; in lateral view, pronotal suture marked; lateral dorsopropodeal processes (ldpp) long, covering propodeal spiracle in dorsal; propodeal spines of moderate size, slightly longer than the distance between their apices, in dorsal view propodeal spines diverge; in lateral view, propodeal spines curved; propodeal spiracle large, circular, projecting posterodorsally, diameter (0.071 mm) approximately equal to length of third and fourth antennomere; propodeal lobe angulate, apex blunt.

Metasoma. In dorsal view, petiole rectangular, anterior and posterior margins of petiole of equal length; lateral margins of petiole parallel, twice the size of anterior margin; lateral margins of petiole node with 1 posterolateral tubercle on each side; in lateral view, petiole trapezoidal, peduncle and petiole node without apparent differentiation forming a continuous outline, extending to dorsal surface of petiole node; anterior surface of petiole with anteromedial petiolar spine on each side, superior to petiole spiracle; dorsal surface weakly rounded and short; anteroventral process of petiole broad, triangular in shape; in dorsal view, postpetiole cup-shaped, twice as wide as long; in lateral view postpetiole globose, taller than long.

Sculpture. Dorsal surface of head mostly smooth and shiny, with a striate area restricted to the lower part of the frontal area, between the antennal insertions and the eyes; dorsal surface of mandibles smooth and shiny, with slight striation restricted to inner margin; clypeus smooth and shiny; scapes smooth and shiny; dorsum of mesosoma with longitudinal striations extending over entire surface; lateral surface of mesosoma smooth and shiny, with longitudinal striation restricted to lower margin; dorsum of petiole and postpetiole smooth and shiny; gaster smooth and shiny.

Pilosity and color. Dorsal surface of body with erect hairs, separated by a distance less than the length; erect hairs as long as the length of propodeal spines; in full-face view, head capsule with simple, erect to suberect hairs; scapes covered with erect hairs as long as the maximum width of the scape; antennae and mandibles pale brown; propodeal spines and legs with erect hairs equal to the length of propodeal spines; gaster with abundant erect hairs, separated by a distance less than its length.

Natural history.

Ants were collected in lowlands, foraging on the ground and in leaf litter.

Comments.

According to Longino (2006), N. vargasi and N. pleuriticus are parapatric species differentiated by the sculpture of the body surface, much smoother and shinier in N. vargasi . The latter is distributed in humid forests at medium elevations of ~ 1100 m, while N. pleuriticus lives in lowlands, below 500 m. In Colombia, the populations of N. vargasi and N. pleuriticus present a sympatric distribution since workers of both species were collected as foragers on the vegetation in the same fragment of TDF in the Tuparro National Natural Park (Vichada). This record increases the distribution range of N. vargasi from 135 m in the tropical dry forest to 1100 m in humid forest.

The examined workers of N. vargasi fit the definition of Longino (2006), with a smooth and shiny body, although they are slightly paler in color. Sympatric populations of N. pleuriticus and N. vargasi show variation in size, sculpture, coloration and shape of the petiole and postpetiole, exhibiting contrasting characteristics between both species, reaffirming the description of N. vargasi by Longino (2006). This record expands the distribution of N. vargasi , being the first report for South America.

Figures

Figure 27. Nesomyrmex vargasi worker (CBUMAG: ENT: 41665) A full-face view B lateral view C dorsal view. Scale bars: 0.5 mm.

Figure 29. Distributional map of Nesomyrmex species from the tropical dry forest in Colombia.