Royidris peregrina Bolton & Fisher

Bolton, Barry & Fisher, Brian, 2014, The Madagascan endemic myrmicine ants related to Eutetramorium (Hymenoptera: Formicidae): taxonomy of the genera Eutetramorium Emery, Malagidris nom. n., Myrmisaraka gen. n., Royidris gen. n., and Vitsika gen. n .., Zootaxa 3791 (1), pp. 1-99 : 61-62

Royidris peregrina Bolton & Fisher sp. n.

(Figs 66-68, Map 144)

WORKER (holotype in parentheses). TL 2.6-3.3 (2.9), HL 0.62-0.76 (0.72), HW 0.52-0.67 (0.60), CI 84-88 (85), SL 0.60-0.72 (0.65), SI 108-118 (108), PW 0.34-0.44 (0.40), WL 0.76-0.96 (0.88) (18 measured).

Antennal club 4-segmented. Mandible longitudinally costulate. Scapes of moderate relative length (SI 108-118; mean SI 113); when laid straight back in full-face view the apex of the scape distinctly surpasses the posterior margin of the head. With head in full-face view the eyes at the midlength of the side of the head capsule. EL 0.16-0.21 (EL/HW 0.30-0.33). Dorsum of head from level of eyes to posterior margin varies from finely reticulate-punctate to almost unsculptured; the sculpture sometimes uniform but frequently reduced in density and intensity dorsolaterally, or effaced in places, or mostly effaced. Promesonotum in profile convex and swollen, the mesonotum posteriorly descends abruptly to a small, weakly incised metanotal groove. In absolute profile the propodeal dorsum is horizontal and flat, or very nearly flat; posteriorly dorsum meets the declivity in a rounded right-angle and the declivity is straight and almost vertical. The whole propodeal dorsum is strongly depressed with respect to the highest point of the promesonotum, which is on a considerably higher level. Pronotum with 3-5 pairs of setae; mesonotum with 3-4 pairs; dorsum of propodeum without setae; petiole node with 2 pairs, one apical, the other on the posterior face; postpetiole with setae dorsally and posteriorly; first gastral tergite with numerous suberect setae. All setae are shorter than the maximum vertical diameter of the eye. Dorsum of pronotum smooth to weakly, superficially reticulate, distinctly less strongly sculptured than the finely reticulate-punctulate propodeal dorsum. Side of pronotum reticulate to weakly reticulate-punctulate, this sculpture less strong than on the densely reticulate-punctate mesopleuron. Metafemur with MfL 0.60-0.74 (MfL/HW 1.08-1.13, MfL/MfH 3.50-3.76). Postpetiole relatively narrow in dorsal view, maximum width 0.16-0.20 (0.30-0.31 x HW). Sides of petiole and postpetiole nodes weakly reticulate-punctulate; dorsum of postpetiole unsculptured. First gastral tergite glassy smooth, without superficial microreticulation. Colour of mesosoma, petiole and postpetiole variable, yellowish brown, orange-brown or medium brown, the head usually somewhat darker than the mesosoma; the gaster always much darker, very dark brown to black.

QUEEN (gyne). Alate when virgin. Much larger than worker. TL 5.5, HL 0.98, HW 0.84, CI 94, SL 0.78, SI 93, PW 0.68, WL 1.63, EL 0.29 (EL/HW 0.35), MfL 0.84 (MfL/HW 1.00, MfL/MfH 3.82), maximum dorsal length of mesoscutum 0.78, maximum width of mesoscutum 0.74, maximum dorsal width of postpetiole 0.43 (0.51 x HW) (1 measured). Head more coarsely reticulate-punctate than in the worker, and also with fine longitudinal striolae. Mesoscutum more or less smooth along the midline, but on either side with disorganised superficial reticulate-punctation, upon which are superimposed scattered larger punctures. Mesoscutellum with similar but much reduced sculpture, almost smooth. Propodeal dorsum reticulate-punctate and with fine transverse costulae. Petiole, postpetiole and first gastral tergite finely reticulate-punctate, on the first gastral tergite the sculpture densest and coarsest in the basal half, becoming weaker and more superficial posteriorly. Side of pronotum and mesopleuron very weakly reticulate-punctate, metapleuron and side of propodeum much more strongly so. Propodeum terminates in a pair of broadly triangular, tooth-like angles. All dorsal surfaces except propodeum with numerous fine setae; propodeum has one erect pair present. Colour as in worker.

MALE. Known from only two specimens; gaster of the first missing, head and gaster of the second missing. Smaller than worker, much smaller than queen. HL 0.47, HW 0.41, WL 0.94. Head not dorsoventrally flattened, the clypeus bulging in profile. Ocelli at highest point of vertex; outline of dorsum descends steeply behind ocellus to the sharp occipital carina; with head in profile the length of the cephalic dorsum between the posterior ocellus and the occipital carina is greater than the length of the ocellus. See also under diagnosis of genus.

Holotype worker, Madagascar: Makay Mts, 21.34109°S, 45.18054°E, 500 m., 28.xi.2010, BLF 25314, CASENT0209249, barren rock with sparse vegetation, burned grass (B.L. Fisher et al.) (CASC).

Paratypes. 2 workers with same data as holotype but one BLF 25303, CASENT0209248, the other BLF 25318, CASENT0203840 (CASC).

This species closely resembles gravipuncta , but has much less strongly developed sculpture, and has relatively slightly longer scapes and metatibiae (SI and MfL/HW in gravipuncta 95-107, and 0.95-1.05, respectively). In addition, peregrina has the dorsum of the postpetiole unsculptured, and the first gastral tergite is glassy smooth, lacking superficial microreticulation. In gravipuncta the dorsum of postpetiole is superficially reticulate-punctulate, and the first gastral tergite is usually obviously superficially microreticulate, at least on the basal half and usually everywhere.

As well as being found running on barren rocks, this species has also been discovered in savannah shrubland and burned savannah.

Non-paratypic material examined. Madagascar: Prov. Toliara, Makay Mts (B.L. Fisher et al.); Prov. Mahajanga, Res. forest Beanka (B.L. Fisher et al).