Royidris gravipuncta 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 : 53-55

Royidris gravipuncta Bolton & Fisher sp. n.

(Figs 54-56, Map 140)

WORKER (holotype in parentheses). TL 3.0-3.6 (3.5), HL 0.68-0.84 (0.79), HW 0.58-0.72 (0.70), CI 84-89 (89), SL 0.61-0.72 (0.70), SI 95-107 (100), PW 0.39-0.46 (0.45), WL 0.88-1.05 (0.97) (28 measured). Antennal club 4-segmented. Mandible longitudinally costulate. Scapes of short to moderate relative length (SI

95-107; mean SI 101); when laid straight back in full-face view the apex of the scape slightly 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 0.19-0.23 (EL/HW 0.31-0.33). Dorsum of head from level of eyes to posterior margin strongly, evenly reticulate-punctate. On each side of the cephalic midline, especially in larger individuals, the margins of the punctures may be aligned, and produce the impression of fine longitudinal striolae. The sculpture does not fade in density and intensity dorsolaterally or posteriorly. 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 3-4 pairs of setae; mesonotum with 3-5 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. Entire dorsum of mesosoma finely and densely reticulate-punctate, the sculpture of about equal density and intensity everywhere. Pronotum sometimes also with weak transverse striolae, especially in larger individuals. Entire side of mesosoma finely and densely reticulate-punctate, the sculpture of equal density and intensity everywhere. Metafemur with MfL 0.60-0.72 (MfL/HW 0.95-1.05, MfL/MfH 3.20-3.44). Peduncle of petiole usually unarmed behind the minute subpetiolar process, but in one aberrant paratype there is an elongate, fine cuticular tooth posterior to the process. Postpetiole relatively narrow in dorsal view, maximum width 0.18-0.23 (0.29-0.34 x HW). Sides of petiole node and postpetiole reticulate-punctulate; dorsum of postpetiole superficially reticulate-punctulate. First gastral tergite superficially microreticulate, at least on the basal half; in most workers the microreticulation is distinct, but in some it is reduced to a faint superficial patterning. Colour of mesosoma, petiole and postpetiole orange-brown to dull reddish brown, the head usually somewhat darker than the mesosoma; the gaster always darker, glossy dark brown to almost black.

QUEEN and MALE: unknown.

Holotype worker (top specimen of three on pin), Madagascar: Prov. Toliara, P.N. Tsimanampetsotsa, Mitoho, 6.4 km. 77° ENE Efoetse, 24°03'S, 43°46'E, 40 m., 18-22.iii.2002, BLF 6164, CASENT0485033, at light, spiny forest thicket (Fisher et al.) (CASC).

Paratypes. 11 workers with same data as holotype but CASENT0485008, CASENT0485032, CASENT0485034, CASENT0485041, CASENT0485042 (CASC, BMNH).

Material treated as the single species shuckardi by Heterick (2006) is here divided into three species. The main mass of this material is now regarded as gravipuncta , but a couple of specimens have much longer and denser setae and have been removed to a separate species, longiseta . An isolated queen, the only specimen that genuinely represents shuckardi , can not be associated with either of these worker-based taxa for reasons discussed under shuckardi .

R. gravipuncta is the most evenly, densely sculptured species in the genus. The entire dorsal head, and the whole mesosoma, dorsally and laterally, are strongly reticulate-punctate; the density and intensity of the sculpture is consistent on all these surfaces.

The most obvious difference between gravipuncta and longiseta concerns the setae of the promesonotum and first gastral tergite. In gravipuncta the setae are distinctly shorter than the maximum vertical diameter of the eye, whereas in longiseta they are obviously longer than the vertical diameter of the eye. In addition, the available specimens of longiseta have erect short setae on the propodeum, tend to be somewhat smaller (HW 0.54-0.56), and the sculpture is not as intense or consistently dense as in gravipuncta .

The relationship of gravipuncta to peregrina is very close. The latter appears as a much less densely sculptured version of the former, which also has relatively longer scapes and metatibiae. Unfortunately, the clarity of this division is blurred by four workers from Beanka. Among all the material retrieved from that locality, these four specimens have measurements that are within the gravipuncta range (SI 103-107, MfL/HW 1.00-1.06), but exhibit sculpture that is strikingly less dense and uniform than that shown in all other gravipuncta material. Their sculpture is however, stronger than is seen in peregrina , and microreticulation is retained on the first gastral tergite. For the present, these specimens are tentatively referred to gravipuncta , but the possibility that they constitute a separate species, or may indicate that gravipuncta and peregrina should really be regarded as a single, very variable species, must await later analysis, when more material of possible intermediate forms has become available.

This species has been collected in an urban garden, but is usually found in spiny forest, where it has been collected from under stones, as ground foragers, from pitfall traps, and from dead twigs on the ground. It may also be found in savannah shrubland and in Bismarckia woodland. The type-series was retrieved from a light trap in spiny forest, indicating that it forages by night as well as by day, and that it ascends objects that rise from the forest floor.

Non-paratypic material examined. Madagascar: Prov. Toliara, P.N. Tsimanampetsotsa, Bemanateza (Fisher et al.); Prov. Toliara, Betroka (B.L. Fisher et al.); Prov. Toliara, Foret Mahavelo, Isantoria Riv., NE Ifotaka (Fisher et al.); Prov. Toliara, Mahafaly Plateau, ENE Itampolo (Fisher et al.); Prov. Toliara, Tsihombe (Fisher et al.); Prov. Toliara, Tsivory (Fisher et al.); Prov. Toliara, Amboasary (Fisher et al.); Prov. Mahajanga, Res. forest Beanka (B.L. Fisher et al.); Prov. Fianarantsoa, P.N. Isalo, Isalo II (A. Ravelomanana); Prov. Fianarantsoa, Ranohira, Ampandravelo III (A. Ravelomanana); Tulear Berenty Special Reserve ( Rin’Ha & Irwin).