Polyrhachis longiseta, 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) : 28-30

Polyrhachis longiseta n. sp.

( Figures 8 a–c)

Diagnosis. A small species in the revoili -group with evenly convex anterior clypeal margin, reduced pronotal teeth, unarmed propodeum, and abundant long standing hairs on body and appendages.

Holotype worker. HL 1.22, HW 1.02, CI 84, SL 1.44, SI 141, FW 0.37, FI 36, PW 0.74, WL 1.51, HTL 1.20.

Clypeus medially weakly carinate and with its anterior margin evenly convex. Head in full face view oval, with anteriorly converging sides and convex posterior margin. Eyes moderately developed and convex. Mesosoma stout, fully immarginate, evenly convex in profile. Pronotal teeth minute, their anterior edge perpendicular to the longitudinal body axis. Propodeal dorsum and declivity in profile meeting at a blunt obtuse angle, without teeth or ridges. Promesonotal suture clearly visible, metanotal suture faint. Petiole with a dorsal pair of moderately long, slightly diverging spines and a lateral pair of small teeth; the space between dorsal spines evenly and shallowly concave. First gastral tergite anteriorly weakly concave.

Mandibles smooth and shining with sparse piligerous pits. Head, mesosoma and petiole mostly irregularly reticulate-punctate. Head, except clypeus, with a superimposed mostly longitudinal rugosity. Mesosomal dorsum mostly finely longitudinally rugulose. Appendages finely reticulate-punctate. Head, mesosoma and appendages moderately shining. Gaster superficially reticulate and shining.

Standing hairs of uneven length, pale, flexuous and abundant on body and appendages. Longest hairs on tibiae exceed the maximum tibial width; longest hairs on scapes are four times as long as the scape diameter at midlength, or even longer. Pubescence whitish, moderately long and dense on most body surfaces.

Body black, mandibles, legs and scapes mostly piceous, mandibles apically ferrugineous. Funiculus almost entirely testaceous, except its proximally darkened basalmost joints.

Paratype. HL 1.19, HW 0.95, CI 80, SL 1.30, SI 137, FW 0.38, FI 40, PW 0.73, WL 1.42, HTL 1.15. A single worker from the Rep. of the Congo shares all main feature with the holotype.

Holotype. CAMEROUN: Mbalmayo, xi.1993 (N. Stork) (BMNH, specimen tagged “B.Mec, 1 (2)”).

Paratype. REP. of the CONGO: Niari Region, 2.30921 S 12.82224 E, 754 m, 4.vii.2013–9.vii.2013, primary forest, canopy fogging (L. Niemand) (1 w, AFRC: LN-RC1-045, CASENT0250168).

Comment. Polyrhachis longiseta comes from the same locality as P. dubia and these species look very similar; the relative length of standing hairs is a good feature to separate them. In P. longiseta the longest hairs on tibiae clearly exceed the maximum tibial width and this feature distinguishes it from P. dubia and other species in the revoili -group with a convex anterior clypeal margin and immarginate mesosoma, i.e. lanuginosa , revoili and weissi . All of these are also more strongly sculptured than longiseta .

Figures

FIGURE 8. Polyrhachis longiseta, holotype worker: A, body profile; B, dorsum of mesosoma; C, head in full-face view. (Photos by M. Zilioli)