Nesomyrmex inhaca, Garcia & Mbanyana & Audisio & Alpert, 2017

Garcia, Francisco Hita, Mbanyana, Nokuthula, Audisio, Tracy Lynn & Alpert, Gary D., 2017, Taxonomy of the ant genus Nesomyrmex Wheeler (Formicidae, Myrmicinae) in the Afrotropical region, with a review of current species groups and description of a new species of the N. angulatus group from Mozambique, European Journal of Taxonomy 258, pp. 1-31 : 22-25

Nesomyrmex inhaca sp. nov.

urn:lsid:zoobank.org:act:C33B5A40-C3C0-4860-BD38-C99AC2D774A3

Figs 11 A–B, 18

Diagnosis

The following character combination distinguishes N. inhaca sp. nov. from the other members of the N. angulatus group: in profile mesosomal dorsum with conspicuously impressed metanotal groove; in dorsal view petiolar node not laterally denticulate; dorsum of propodeum without standing hairs; first gastral tergite with standing hairs evenly distributed throughout.

Etymology

The new species is named after the type locality, Inhaca Island, to the southeast of Mozambique. The species epithet is a noun in apposition and thus invariant.

Type material

Holotype

MOZAMBIQUE: pinned worker, Maputo, Inhaca Island , 26°2′9″ S, 32°54′17″ E, 1 m, secondary forest, low vegetation, 21 Jun. 1992, G.D. Alpert leg. (MCZC: MCZ-ENT00593557 ).

Paratypes

MOZAMBIQUE: 6 pinned workers, same collection data as holotype ( BMNH: CASENT0790018;

HLMD: HLMD-Hym-2395; KSMA: CASENT0790019; MCZC: CASENT0790017; SAMC: CASENT0790022; ZFMK: CASENT0790020).

Worker measurements (n=7)

HL 0.69–0.73 (0.71); HW 0.50–0.53 (0.51); SL 0.47–0.51 (0.50); EL 0.16–0.17 (0.17); PH 0.26–0.28 (0.27); PW 0.41–0.42 (0.41); WL 0.85–0.88 (0.87); PSL 0.12–0.13 (0.12); PTL 0.14–0.16 (0.15); PTH 0.21–0.22 (0.22); PTW 0.19–0.20 (0.19); PPL 0.18–0.20 (0.19); PPH 0.21–0.22 (0.21); PPW 0.27–0.28 (0.28); CI 71–73 (72); SI 95–98 (96); OI 30–33 (32); DMI 47–49 (48); LMI 31–32 (32); PSLI 16–18 (17); LPeI 64–70 (69); DPeI 127–141 (131); LPpI 86–93 (89); DPpI 140–147 (145); PPI 138–147 (143).

Worker description

HEAD. Masticatory margin of mandible with five teeth, decreasing in size from largest, acute apical tooth to smallest basal denticle; clypeus arched-convex to almost triangular, anterior margin with slightly darker, lamellate, flattened ridge all-around; head in full-face view appearing relatively narrow, much longer than broad (CI 71–73), sides of head approximately straight, gently broadening behind eye level, narrowest directly behind posterior eye margin, and widest halfway between posterior eye margin and posterior head margin; posterior head margin concave medially; frontal carinae and antennal scrobes absent; antennal scapes moderately long, not reaching posterior head margin (SI 95–98). Eyes relatively large (OI 29–33), with eight to nine ommatidia in the longest row.

MESOSOMA. In lateral view mesosomal outline relatively low (LMI 31–32) and flat with conspicuously impressed metanotal groove; promesonotal suture present laterally and completely absent dorsally; pronotum moderately marginate between lateral and dorsal mesosoma, anterodorsal corners not denticulate; propodeum armed with short to moderately long propodeal spines (PSLI 16–18), in profile spines distinctly longer than their basal width; propodeal lobes low and rounded.

WAIST SEGMENTS AND GASTER. Petiolar peduncle long, anteriorly with a small tooth-like subpetiolar process; in profile petiolar node relatively low and globular, between 1.4 and 1.5 times as high as long (LPeI 64–70); anterior face smoothly merging with peduncle and petiolar dorsum without any angles, posterior face slightly better developed; node in dorsal view about 1.3 to 1.4 times as wide as long (DPeI 127–141); in dorsal view petiolar node not laterally denticulate; in profile postpetiole globular, about 1.1 to 1.2 times as high as long (LPpI 86–93); in dorsal view about 1.4 and 1.5 times as wide as long (DPpI 140–147); postpetiole in dorsal view around 1.4 to 1.5 times as wide as petiolar node (PPI 138–147).

SCULPTURE. Mandibles shagreened to partly smooth and shiny, sometimes with very weak, superficial, irregular, longitudinal rugulae; median clypeal carina present and conspicuous, usually accompanied by one or two lateral, longitudinal, and slightly weaker rugae on each side; cephalic dorsum posteriorly and laterally strongly reticulate-rugose, medially more irregularly longitudinally rugose, ground sculpture conspicuously reticulate-punctulate; mesosoma laterally and dorsally with distinct reticulate-punctulate ground sculpture, lateral mesosoma conspicuously reticulate-rugose, dorsum reticulate-rugose with some irregular, longitudinal elements medially; legs unsculptured, smooth and shining; petiole and postpetiole with irregular reticulate-rugose sculpture superimposed on reticulate-punctulate ground sculpture; sculpture of first gastral tergite variable, some specimens only with reticulate-punctulate ground sculpture, other specimens irregularly rugose/rugulose on top of reticulate-punctulate ground sculpture.

PILOSITY AND PUBESCENCE. Head, mesosoma, waist segments and gaster dorsally with sparse, erect, blunt, and moderately long pilosity, hairs shorter on head and mesosoma than on waist segments and gaster; head laterally and ventrally with short appressed to decumbent pubescence; pubescence on mesosoma and waist segments sparse to absent; first gastral tergite with short to moderately long, appressed to decumbent pubescence.

COLORATION. Body uniformly yellowish to light brown, in a few specimens legs slightly lighter yellow, almost white.

Diagnostic comments

Within the members of the N. angulatus species group, N. inhaca sp. nov. cannot be mistaken for N. evelynae since the latter is devoid of standing hairs on the first gastral tergite except for a single transverse row on the posterior end of the tergite, and also has very long propodeal spines and a relatively high petiolar node. Nesomyrmex inhaca sp. nov. has short, standing hairs evenly distributed throughout the first gastral tergite, shorter propodeal spines and a much lower petiolar node. The species pair N. angulatus and N. grisoni both do not possess a trace of a metanotal groove, which is obviously present in N. inhaca sp. nov. and thus it is not likely these species will be confused. Nevertheless, N. inhaca sp. nov. is morphologically closer to the trio of species N. denticulatus , N. innocens and N. stramineus . These three are, however, easily separable since they possess a petiolar node with distinct lateral denticles and have standing hairs on the propodeal dorsum, while N. inhaca sp. nov. lacks both the lateral petiolar denticles and the standing hairs on the propodeum. Moreover, N. inhaca sp. nov. has apparently longer antennal scapes based on the much higher SI (94–95) compared to the other three species (SI 67–77). This is partly due to the fact that N. inhaca sp. nov. has indeed relatively longer antennal scapes, but the comparatively narrow head with low values of HW contributes to these high SI values. Therefore, we suggest being cautious with scape length as the single diagnostic character.

Intraspecific variation

Since the description is based on just one collection event, the observed intraspecific variation seen in the worker caste is very low. However, the sculpture on the first gastral tergite shows some variability, as described above.

Biology

Nesomyrmex inhaca sp. nov. was sampled from low vegetation in secondary forest at an elevation of 1 m. Apart from this, nothing is known of its natural history.

Distribution

The new species is so far only known from one collection event on Inhaca Island in the southeast of Mozambique. Despite this apparently restricted distribution to just one island, we are reluctant to declare N. inhaca sp. nov. as endemic to Inhaca Island. With the noticeable exception of the area around Gorongosa, most of Mozambique remains severely under-sampled and our knowledge of local ant communities and species distributions is very poor to non-existent. Consequently, it is possible that N. inhaca sp. nov. will also be found on the mainland.

Figures

Fig. 11. Waist segments in dorsal view and mesosoma in profile. A–B. Nesomyrmex inhaca sp. nov. (CASENT0790016). C. N. denticulatus (Mayr, 1901) (CASENT0914923). D. N. denticulatus (Mayr, 1901) (CASENT0908992).