Nesomyrmex iku, Arredondo & 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 iku sp. nov.

Figs 22 , 29

Type material.

Holotype. Colombia • 1 worker; Magdalena, Santa Marta, Sierra Nevada de Santa Marta ; 10.816667°N, 73.650000°W; IAvH -E-75014 [ IAvH] . Paratype (n = 1). 1 worker; same data as holotype; IAvH -E-75007 ( CBUMAG) .

Geographic range.

Colombia.

Holotype worker measurements.

HL 0.86, HW 0.73, SL 0.63, ML 0.34, EL 0.18, PW 0.48, PTW 0.25, PPW 0.28, WL 1.13, PH 0.34, PTL 0.47, PTH 0.30, PPL 0.3, PPH 0.29, GL 0.91. CI 85, SI 86.

Paratype worker measurements.

(n = 1) HL 0.89, HW 0.74, SL 0.63, ML 0.35, EL 0.18, PW 0.48, PTW 0.26, PPW 0.30, WL 1.18, PH 0.35, PTL 0.48, PTH 0.30, PPL 0.32, PPH 0.29, GL 0.96. CI 85, SI 86.

Diagnosis.

Mesosomal dorsum straight. Lateral margins of pronotum rounded, converging towards mesonotum. Lateral margins of mesonotum and dorsopropodeum with slightly angled lateral projections. Lateral dorsopropodeal processes short, not covering spiracle in dorsal view.

Description.

Worker. In full-face view, head longer than wide (CI 84–85), lateral margins straight, slightly curved posterior to the eyes, continuing into occipital margin, weakly convex mesally; mandible triangular, masticatory margin of mandible with five teeth, separated from basal margin by fifth tooth; anterior clypeal margin convex, projecting above the mandibles; lateral eyes protruding, below half the length of the head, with 11 ommatidia at their greatest diameter; full-face view, frontal lobes not prominent and weakly rounded, partially covering antennal insertions; frontal carina extending to anterior margin of eye; antenna with 12 antennomeres, 3 - segmented club; scape curved at base, relatively long (SI 85–86) but not reaching the occipital margin by a distance almost twice its apical width; pedicel longer than wide, almost as long as the next three antennomeres together.

Mesosoma. In lateral view, mesosomal profile straight; in dorsal view, pronotum wider than long, maximum width towards anterior margin, the latter slightly convex; humeral angles angulate; lateral margins of pronotum curved posteriorly; in lateral view, promesonotal suture marked; in dorsal view, lateral mesonotal and dorsopropodeal projections slightly angulated; propodeal spines divergent, longer than half the distance between their apices; propodeal spiracle small, circular, projecting posterodorsally; propodeal lobe short and uniformly rounded.

Metasoma. In dorsal view, petiole trapezoidal with anterior portion narrower than posterior portion, lateral margins diverging posteriorly; in lateral view, peduncle and petiole node without apparent differentiation, forming a continuous outline, extending to dorsal face of petiole node; anterior face of petiole with anteromedial petiolar spine above petiolar spiracle; dorsal surface weakly rounded and short, continuing with a straight posterior face; anteroventral process of petiole pyramidal; in dorsal view, postpetiole oval, slightly wider than long, in lateral view postpetiole globose, taller than long.

Sculpture. Body generally opaque; body surface rugose-reticulate, excluding smooth, shiny gaster; clypeus with medial longitudinal costae; dorsal surface of mandible, scapes, and legs weakly punctate and shiny.

Pilosity and color. Dorsal surface of body with flattened erect hairs, mostly separated by a distance equal to or greater than their length, hairs as long as base of propodeal spines; in full-face view, scapes partly covered with short decumbent hairs, no erect hairs present; legs devoid of erect hairs, with sparse simple decumbent hairs restricted to apex of femur; gaster with sparse erect hairs, separated from each other by a distance twice their length. Body concolorous yellow.

Queen and male.

Unknown.

Natural history.

No related information.

Etymology.

The name of this species refers to the Arhuaco people with ancestral lands close to the type locality of the species. The Arhuaco people self-identify as Iku, which translates as “ people ” in the Ika language ( Tracy 1997). Iku (Arhuacos) - Guardians of life, defenders of the peaceful coexistence of men among themselves and with the forces of nature. This is a name in apposition and thus invariable.

Comments.

This species is only known from the type material. Nesomyrmex iku sp. nov. is easily recognized by the shape of the straight mesosomal profile and by the lateral dorsopropodeal processes short, not covering spiracle in dorsal view. Morphologically, the closest species is Nesomyrmex xerophilus sp. nov., but they can be differentiated mainly by the lateral projection of the frontal lobes, the latter being wider posterior to the torulus, whereas N. iku does not have such a projection on the frontal lobes. On the other hand, in N. xerophilus the propodeal spiracles are not visible in dorsal view, since the lateral portion of the dorsopropodeal projects above them, whereas in N. iku the propodeal spiracles are visible in dorsal view.

Another species with similar morphology is N. brasiliensis . When comparing the type workers of N. iku ( IAvH -E-75014 , IAvH -E-75007 ) with the type ones of N. brasiliensis ( MZSP 87370, MZSP 87374) we found that both species share a straight mesosomal profile, petioles and postpetioles lacking tubercles and body concolorous yellow. However, they differ in several features: The antennal flagellum of N. iku has 12 antennomeres, while N. brasiliensis has 11; additionally, the sculpture of the frontal area in N. brasiliensis is foveated in contrast to the frontal area striated in N. iku . Other distinguishing characteristics include the length of the propodeal spines, and the size and shape of the antennal scapes. A more extensive discussion on the similarity of N. brasiliensis , N. iku , and N. xerophilus will be possible when more material can be analyzed.

Figures

Figure 22. Nesomyrmex iku sp. nov. Holotype worker (IAvH - E- 75014) 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.