Nesomyrmex xerophilus Arredondo-H & Guerrero, 2025

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 xerophilus Arredondo-H & Guerrero sp. nov.

Figs 28 , 29

Type material.

Holotype. Colombia • 1 worker; Magdalena, Santa Marta, Vda. Puerto Mosquito, Reserva la Iguana Verde ; 11.176972°N, 74.185167°W; 02 Nov. 2019; M. Escárraga leg.; Manual capture; CBUMAG:ENT:12440 [ CBUMAG] . Paratypes (n = 14). Colombia • 8 workers; same data as holotype; CBUMAG:ENT:12441 ( ICN), CBUMAG:ENT:41656 ( CBUMAG), CBUMAG:ENT:42097 ( CBUMAG), CBUMAG:ENT:42098 ( CBUMAG), CBUMAG:ENT:42099 ( CBUMAG), CBUMAG:ENT:42100 ( CBUMAG), CBUMAG:ENT:42101 ( CBUMAG), CBUMAG:ENT:42102 ( MEFLG) . • 1 worker; Cesar, Valledupar, Cgto. Los Corazones, PNR Los Besotes ; 10.572165°N, 73.271218°W; 584 m a. s. l.; 14 16 Sep. 2023; H. Sierra, L. Ramos, R. Guerrero y S. De La Hoz legs.; Winkler; CBUMAG:ENT:41655 ( CBUMAG) . • 2 workers; Magdalena, Santa Marta, Reserva Caoba ; 11.213139°N, 74.101667°W; 27 Nov. 2018; M. Escárraga leg.; CBUMAG:ENT:12164 , CBUMAG:ENT:12165 ( CBUMAG) . • 1 worker; Magdalena, Santa Marta, Cerro Taganga ; 11.259111°N, 74.180139°W; 117.3 m a. s. l.; 03 Mar. 2007; D. Ramírez y D. Olivero-G legs.; Pitfall; CBUMAG:ENT:12163 ( IAvH) . • 2 workers. Magdalena, Santa Marta, Ciénaga, 5 km SE, Río Frío ; 10.883306°N, 74.133333W; 100 m a. s. l.; 16 ago. 1985; P. Ward leg.; ICN 019704 ( ICN) .

Geographic range.

Colombia.

Holotype worker measurements.

HL 0.69, HW 0.6, SL 0.44, ML 0.29, EL 0.15, PW 0.43, PTW 0.28, PPW 0.37, WL 0.88, PH 0.23, PTL 0.23, PTH 0.25, PPL 0.22, PPH 0.23, GL 0.66 CI 86, SI 0.73.

Paratype worker measurements.

(n = 4) HL 0.69–0.7, HW 0.59–0.6, SL 0.43–0.44, ML 0.29, EL 0.15–0.16, PW 0.43–0.44, PTW 0.28–0.29, PPW 0.36–0.37, WL 0.9–0.91, PH 0.22–0.23, PTL 0.23–0.27, PTH 0.24–0.25, PPL 0.22–0.23, PPH 0.23–0.24, GL 0.66–0.68, CI 85–86, SI 72–73.

Diagnosis.

Frontal lobe projected laterally, covering the antennal insertions. Frontal carina extending to posterior cephalic vertex, forming a weak scrobus. Dorsum of mesosoma straight and flattened. Lateral margin of pronotum straight, converging towards mesonotum. Lateral projection of the mesonotum dentate. Lateral dorsopropodeal processes long, covering propodeal spiracle in dorsal view.

Description.

Worker. In full-face view, head longer than wide (CI 85–86), slightly narrowing behind the eyes; occipital margin weakly convex; occipital angles rounded; lateral margins slightly curved posteriorly; anterior margin of clypeus weakly convex, projecting over mandibles; eyes lateral, with 10 ommatidia at greatest diameter; frontal lobes laterally expanded, antennal insertions completely hidden by frontal lobes; frontal carina extending to posterior cephalic vertex, as if forming a weak scrobus; antenna with 12 antennomeres; mandible triangular; inner margin with five teeth, separated from basal margin by fifth tooth; scapes short (SI 72–73) barely reaching posterior margin of eye, curved towards mid-length; pedicel longer than wide, and almost as long as next three antennomeres together; antennal club with three antennomeres.

Mesosoma. In lateral view, mesosomal profile straight; in dorsal view, pronotum wider than long, with its maximum width towards anterior margin, the latter slightly convex, humeral angle angulated, lateral margins of pronotum curved; in lateral view, promesonotal suture present, in dorsal view, absent; in dorsal view, mesosomal lateral projection angulate; dorsopropodeal lateral projection angulate, projecting over propodeal spiracles; propodeal spines short, less than half the distance between their apices in length, and divergent; in lateral view, propodeal spiracle small (diameter = 0.057 mm), approximately equal to the length of the 10 th antennomere, circular, projected posterolaterally; propodeal lobe short and uniformly rounded.

Metasoma. In dorsal view, petiole trapezoidal, anterior margin shorter than posterior margin; posterior margin with two mesial tubercles of equal length; lateral margins diverging from anterior to posterior margin; lateral margin with two posterolaterals tubercles; in anteroposterior direction, first tubercle poorly developed, length less than half the total length of the following tubercle; in lateral view, petiole subquadrate, peduncle and petiolar node without apparent differentiation, forming a continuous outline, which extends to the dorsal surface of the petiolar node; anterior surface of petiole with anteromedial petiolar spine on each side, superior to the petiolar spiracle; dorsal surface weakly rounded and short; anteroventral process of petiole acute; in dorsal view, postpetiole hexagonal, twice as wide as long; in lateral view postpetiole globose, taller than long.

Sculpture. Body generally opaque, with smooth, shiny areas restricted to gaster; dorsal surface of body rugose-reticulate, excluding gaster; lateral surface of mesosoma reticulate; clypeus smooth and shiny, with medial longitudinal carina; dorsal surface of mandibles shiny, with weakly marked striation; scape and legs shiny with superficial sculpture; gaster weakly imbricate.

Pilosity and color. Dorsal surface of body with flattened erect hairs, mostly separated by a distance equal to or greater than its length; hairs as long as the base of the propodeal spines; in full-face view, head capsule with erect hairs restricted to the clypeus, area between the frontal carinae and vertex; scapes covered with short decumbent hairs, without erect hairs; propodeal spines with erect hairs; legs with simple, appressed, sparse hairs restricted to the apex of the femora; gaster with abundant erect hairs, separated by a distance equal to its length. Body pale yellow, legs slightly paler, base and apex of femur and tibia darker.

Queen and male. Unknown.

Natural history.

This species lives within dead branches of shrub vegetation. Populations are distributed in fragments ~ 100 m altitude. In all cases, the ants were found within dry forest with dense vegetation.

Etymology.

The epithet xerophilus is a word composed of the prefix xero - (from ancient Greek ξηρο - meaning dry) and the suffix - philo or - philus (from ancient Greek φίλος meaning attraction towards). The species epithet refers to the dry habitat where these ants live, that is, the tropical dry forest, a life zone highly threatened by the high rate of deforestation in Colombia. It is a noun in apposition and thus invariant.

Comments.

Species easily recognizable by the lateral expansion of the frontal lobes and the lateral projection of the mesosoma and dorsopropodeum in the form of an angled lobe. Morphologically, the closest species to N. xerophilus is N. iku (see comments on Nesomyrmex iku sp. nov.). N. xerophilus is morphologically similar to N. wilda , with both species exhibiting a lateral projection of the mesonotum dentate, long lateral dorsopropodeal processes covering of the propodeal spiracle in dorsal view. Additionally, they share the shape of the propodeal lobes, coloration, and sculpture. Despite these similarities, N. xerophilus differs from N. wilda in the number of antennomeres, as well as in the shape of the frontal lobes, petiole, and postpetiole.

Unlike N. asper , the position and number of petiolar and postpetiolar tubercles in N. xerophilus remain consistent across its populations, with no variation observed in this characteristic. This stability may be attributed to its limited distribution in the tropical dry forest of the Colombian Caribbean region. In contrast, the variation in the position and number of petiolar and postpetiolar tubercles in N. asper appears to be linked to its altitudinal distribution and geographic location (see comments on N. asper ).

Figures

Figure 28. Nesomyrmex xerophilus sp. nov. Holotype worker (CBUMAG: ENT 12440) A full-face view B lateral view C dorsal view. Scale bars: 0.2 mm (A); 0.5 mm (B, C).

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