Royidris anxietas 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 : 45-47

Royidris anxietas Bolton & Fisher sp. n.

(Figs 39-41, Map 135)

WORKER (holotype in parentheses). TL 2.5-2.8 (2.7), HL 0.56-0.64 (0.63), HW 0.47-0.56 (0.56), CI 84-89 (89), SL 0.52-0.60 (0.56), SI 100-110 (100), PW 0.37-0.40 (0.39), WL 0.76-0.82 (0.80) (6 measured).

Antennal club 3-segmented. Mandible longitudinally costulate. Scapes of relatively moderate length (SI 100-110); 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 0.14-0.16 (EL/HW 0.29-0.31). Dorsum of head from level of eyes to posterior margin superficially but distinctly reticulate-punctulate. This sculpture tends to fade in density and intensity dorsolaterally, where it often appears merely shagreenate. Promesonotum in profile convex and swollen, domed, the mesonotum posteriorly descends abruptly to the commencement of the propodeum; the metanotal groove is absent. In absolute profile the propodeal dorsum, from its junction with the mesonotum, is flat to extremely shallowly convex; posteriorly it meets the declivity in a blunt 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. All specimens appear to show some abrasion, but the maximum seta count would seem to be: pronotum with 2 (or possibly 3) pairs; mesonotum with 2 pairs; dorsum of propodeum with a single short pair, immediately above the propodeal angle (see discussion below); 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 that are shorter than the maximum vertical diameter of the eye. Pronotal dorsum mostly smooth but with vestiges of superficial punctulate sculpture; propodeal dorsum finely reticulate-punctulate, much more strongly sculptured than the pronotum. Lower side of pronotum superficially reticulate-punctulate, this sculpture fading out on the upper half of the side. Mesopleuron and metapleuron weakly reticulate-punctulate. Metafemur relatively long and slender, MfL 0.61-0.66 (MfL/HW 1.17-1.22, MfL/MfH 5.50-5.64). Postpetiole relatively narrow in dorsal view, maximum width 0.17-0.20

(0.33-0.36 x HW). Dorsum of postpetiole with superficial fine punctulae; first gastral tergite unsculptured. Colour variable: head, mesosoma, petiole and postpetiole brown to orange-brown, or the head darker brown than the mesosoma, the gaster black (type-series); or the entire ant dark brown, with the gaster black (other material).

QUEEN and MALE: unknown.

Holotype worker, Madagascar: Makay Mts, 21.29961°S, 45.12919°E, 570 m., 5.xii.2010, BLF 25636, CASENT0205644, dry forest edge and burned savannah (B.L. Fisher et al.) (CASC).

Paratypes. 1 worker with same data as holotype but BLF 25640, CASENT0205648; 1 worker with same locality but 21.31334°S, 45.14525°E, 575 m., 6.xii.2010, BLF 25692, CASENT0206182, burned savannah (B.L. Fisher et al.) (CASC).

After robertsoni , this species has the second most densely sculptured head in the robertsoni group. It is easily separated from robertsoni by the unique shape of the propodeum in that species, its lack of propodeal setae, and its uniform light colour. R. anxietas , like pallida and pulchra , lacks the V-shaped, incised metanotal groove characteristic of clarinodis , but in pallida and pulchra the head is smooth. Within the group, robertsoni and clarinodis together have the metafemora relatively shorter and more incrassate, combined MfL/HW 0.93-1.09, and MfL/MfH 3.67-4.50. R. anxietas , pallida and pulchra have the metafemora relatively longer and more slender, with combined MfL/HW 1.12-1.32, and MfL/MfH 5.50-6.00.

The holotype, one paratype, and one of the three non-paratypic specimens have a conspicuous, short, erect seta on the propodeal dorsum, just anterior to the propodeal angle. The other paratype, and the other two non-paratypic specimens, lack this seta. It is assumed here that the presence of this seta is normal and that its absence represents loss by abrasion. As only six specimens are presently available this is merely a guess; the acquisition of more material is necessary to tell if the guess is accurate, or if the presence or absence of this seta is normal variation within the species. The possibility that the six specimens available may represent two species must also be considered. The three that constitute the type-series are bicoloured, with the mesosoma distinctly lighter than the gaster, while the three non-paratypic specimens are uniformly dark. By itself, colour alone would not be convincing, but the dark form also has a more weakly sculptured head. The significance of these differences cannot be assessed at present, the resolution of the problem must await future investigation when more material of both forms has accumulated. The two specimens from Ambovo Springs were included as part of clarinodis by Heterick (2006).

Most individuals of anxietas have been collected in dry forest edges and burned savannah, but samples have also been retrieved from pitfall traps in uapaca woodland, and once from an urban garden.

Non-paratypic material examined. Madagascar: Prov. Toliara, Makay Mts (B.L. Fisher et al.); Prov. Fianarantsoa, P.N. Isalo, Ambovo Springs, N. Ranohira (Fisher et al.).