Royidris robertsoni

The species has been retrieved from litter samples and pitfall traps in spiny forest.

Identification
A member of the robertsoni species group. Bolton and Fisher (2014) - The most densely and universally sculptured member of the robertsoni group, this species can be immediately characterised by the long, very smoothly rounded, even transition from propodeal dorsum to declivity.

Distribution
Endemic to Madagascar.

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Castes
Known only from the worker caste.

Nomenclature

 *  robertsoni. Monomorium robertsoni Heterick, 2006: 93, figs. 14, 37 (w.) MADAGASCAR. Combination in Royidris: Bolton & Fisher, 2014: 64.

Worker
Bolton and Fisher (2014) - TL 2.4–2.6, HL 0.56–0.62, HW 0.46–0.54, CI 82–87, SL 0.50–0.54, SI 100–109, PW 0.34–0.38, WL 0.66–0.78 (4 measured).

Antennal club 3-segmented. Mandible longitudinally costulate. Scapes of short to relatively moderate length (SI 100–109); when laid straight back in full-face view the apex of the scape just exceeds the posterior margin of the head. With head in full-face view the eyes very close to the midlength of the side of the head capsule. EL 0.12–0.14 (EL/HW 0.24–0.28). Dorsum of head to the level of the posterior margins of the eyes finely, densely shagreenate, with some weak, superficial striolae, the whole surface appearing silky; behind the level of the eyes, close to the posterior margin, the sculpture is mainly of extremely fine, dense transverse striolae. Promesonotum in profile convex and swollen, the mesonotum posteriorly descends abruptly to the commencement of the propodeum; there is no strongly defined, V-shaped metanotal groove. In absolute profile the propodeal dorsum slopes downward posteriorly and rounds evenly into the declivity through a broad, shallow curve, without an angle between dorsum and declivity; the declivity itself continues the outward slope posteriorly, its outline not vertical or concave. 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 1–3 pairs of setae (usually 2); mesonotum with 2 pairs; dorsum of propodeum lacks setae. Promesonotal dorsum shagreenate-striolate; propodeal dorsum shagreenate, sometimes also with feeble striolae present. Side of mesosoma finely shagreenate everywhere, the sculpture tends to be weakest on the side of the pronotum, coarser and sometimes somewhat punctulate on the mesopleuron, and extremely fine and dense on the metapleuron, where it is usually distinctly finer than on the mesopleuron. Metafemur with MfL 0.50–0.58 (MfL/HW 1.07–1.09, MfL/MfH 3.86–4.50). Petiole with a single pair of setae posteriorly, near the apex of the node; postpetiole with setae dorsally and posteriorly; first gastral tergite with numerous suberect setae. Postpetiole relatively narrow in dorsal view, maximum width 0.17–0.20 (0.37 × HW). Dorsum of postpetiole and first gastral tergite unsculptured. Colour uniformly yellow, or the gaster may be paler or partially infuscated.

Type Material
Bolton and Fisher (2014) - Holotype and paratype workers: holotype, MADAGASCAR: Prov. Toliara, Ranobe, 23°02’03’’S, 43°36’43’’E, 30 m., 13–19.ii.2002, Frontier Project, MGF056(5), sifted litter, spiney forest thicket, CASENT0003501; one paratype worker with same data but MGF054; two paratype workers, Prov. Toliara, Mandarano, 23°31’38’’S, 44°05’15’’E, 70 m., 10.v.2002, Frontier project, MGF030, sifted litter, gallery forest [CASC examined].