Polyrhachis dubia, Rigato, Fabrizio, 2016

Rigato, Fabrizio, 2016, The ant genus Polyrhachis F. Smith in sub-Saharan Africa, with descriptions of ten new species. (Hymenoptera: Formicidae), Zootaxa 4088 (1) : 16-17

Polyrhachis dubia n. sp.

( Figures 3 a–c)

Diagnosis. A medium-sized species in the revoili -group, with convex anterior clypeal margin, immarginate mesosoma, minute pronotal teeth, very weak propodeal ridges and relatively abundant fine standing hairs on body and appendages.

Holotype worker. HL 1.47, HW 1.21, CI 82, SL 1.66, SI 137, FW 0.44, FI 36, PW 0.95, WL 1.88, HTL 1.56.

Clypeus ecarinate and with evenly convex anterior margin. Head in full face view oval, with anteriorly converging sides and convex posterior border. Eyes moderately developed and convex. Mesosoma stout, immarginate, in profile more convex anteriorly than posteriorly. Pronotal teeth minute, their anterior edge perpendicular to the longitudinal axis of the body. Propodeal dorsum posterolaterally bearing a pair of weak ridges. Promesonotal suture visible, metanotal suture hardly so. Petiole with a median pair of moderately long, slightly diverging spines and a lateral pair of small teeth. In frontal (or posterior) view the space between the spines evenly shallowly concave. First gastral tergite anteriorly weakly concave.

Mandibles weakly striolate and with sparse piligerous pits. Head, mesosoma and petiole mostly reticulatepunctate. A superimposed irregular rugosity occurs on the head (except clypeus), and a finer, mostly longitudinal irregular rugulosity on the mesosoma. Appendages finely reticulate-punctate and subopaque. Head and mesosoma feebly shining; gaster superficially sculptured and shining.

Standing, pale, thin and flexuous hairs of uneven length are fairly abundant on body and appendages; on average they are slightly shorter on gaster and even shorter on legs and funiculi. Longest hairs on scapes easily surpass maximum scape width, on the tibiae always shorter than maximum tibial width. Pubescence whitish, relatively dense, especially on mesosoma, petiole and gaster; shorter and more regularly arranged on the latter.

Body and coxae black, antennae, mandibles and remaining leg segments mostly ferrugineous. First funicular joint, legs articulations, femora and, above all, tibiae and tarsi infuscated.

Paratype workers (n=6). HL 1.30–1.51, HW 1.13–1.25, CI 83–88, SL 1.57–1.74, SI 138–140, FW 0.40–0.45, FI 35–39, PW 0.81–0.96, WL 1.70–2.00, HTL 1.46–1.66.

Mostly consistent with the holotype. Some variations occur in the degree of darkening of appendages, which, at least partially, keep a ferrugineous or even paler tinge. Smallest specimens lack propodeal ridges and in profile their propodeal dorsum and declivity form a blunt obtuse angle.

Holotype. CAMEROUN: Mbalmayo, xi.1993 (N. Stork) (BMNH, tagged “F.93 C7/44”)

Paratypes. same data as the holotype (6 w, BMNH, two specimens per pin: 4 tagged “F.93 C7/47” and 2 tagged “F.93 C7/48”).

Comment. This is a relatively plain species of the revoili -group, with no clypeal lobe, no mesosomal margination and relatively weak sculpturation. It is similar to longiseta and differences between them are pointed out under the latter. Polyrhachis lanuginosa is also alike, but has stronger sculpturation, denser pubescence and more yellowish hairs.

Figures

FIGURE 3. Polyrhachis dubia, holotype worker: A, body profile; B, dorsum of mesosoma; C, head in full-face view. (Photos by M. Zilioli)