Melophorus macroschismus Heterick, Castalanelli & Shattuck

Heterick, Brian E., Castalanelli, Mark & Shattuck, Steve O., 2017, Revision of the ant genus Melophorus (Hymenoptera, Formicidae), ZooKeys 700, pp. 1-420 : 344-346

Melophorus macroschismus Heterick, Castalanelli & Shattuck sp. n.

Types.

Holotype minor worker from near Warrachuppin 31°02'33"S, 118°46'23"E, Western Australia, April 2007, R. Harris, ant nest sample, salt affected remnant, T1Q5 [JDM32-001578] (WAM). Paratypes: 2 minor workers from 6 miles W of Yellowdine, Western Australia, 2 October 1947, T. Greaves, 7739, only specimens [ANIC32 900028] (ANIC); 2 minor workers from Queen Victoria Spring Nature Reserve 30°22'S, 123°37'E, Western Australia, December 1989, CALM, Pitfall trap, sandplain F2 [JDM32-001537] (WAM).

Diagnosis.

Melophorus macroschismus is one of three members of the M. potteri species-group. Like the other two species, M. macrochismus has a large, oblique propodeal spiracle situated well before the declivitous face of propodeum, the spiracle bisecting much of the propodeum. This species is distinguished from the remaining members of the group by a combination of its palp formula (PF 6,4), its matt general appearance, its oval head capsule, the broadly convex but not protrusive anterior clypeal margin, and the conventional appearance of the mandible (five distinct teeth) as opposed to the aberrant dentition of the other two species in the group.

Minor worker description.

Head. Head approximately oval with straight sides; posterior margin of head planar or weakly convex; frons matt or with weak sheen, microreticulate or microreticulate-shagreenate; frons consisting exclusively or almost exclusively of well-spaced, appressed setae only (small, erect setae, if present, usually confined to ocular triangle or posterior margin of head). Eye moderate (eye length 0.20-0.49 length of side of head capsule); in full-face view, eyes set above midpoint of head capsule; in profile, eye set anteriad of midline of head capsule; eyes elliptical or slightly reniform, or roughly ovoid, eye narrowed posteriad. In full-face view, frontal carinae straight or weakly convex; frontal lobes straight in front of antennal insertion. Anteromedial clypeal margin broadly and evenly convex; clypeal psammophore set at or just above anterior clypeal margin; palp formula 6,4. Five mandibular teeth in minor worker; mandibles triangular, weakly incurved; third mandibular tooth distinctly shorter than apical tooth, but equivalent in length to remaining teeth; masticatory margin of mandibles approximately vertical or weakly oblique. Mesosoma. Integument of pronotum, mesonotum and mesopleuron matt or with weak sheen and microreticulate throughout; anterior mesosoma in profile smoothly rounded anteriad, thereafter pronotum and whole of mesonotum flattened and on same plane as propodeum; erect pronotal setae absent; in profile, metanotal groove shallow, broadly V or U-shaped; propodeum matt or with a weak sheen and microreticulate; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity about 4:3; erect propodeal setae always absent; appressed propodeal setulae short, separated by more than own length and inconspicuous; propodeal spiracle situated nearer to midpoint of propodeum than to its declivitous face, and longer (length ≥ 0.50 × height of propodeum). Petiole. In profile, petiolar node squamiform; in full-face view, shape of petiolar node uniformly rounded; node shining and distinctly shagreenate-microreticulate. Gaster. Gaster weakly shining with indistinct shagreenation; pilosity of first gastral tergite consisting of well-spaced short, inconspicuous, appressed setae only, erect setae always absent. General characters. Colour of foreparts light tan or orange-brown, gaster brown.

Measurements.

Worker (n = 6): CI 92-95; EI 28-30; EL 0.21-0.22; HL 0.75-0.83; HW 0.68-0.79; ML 1.06-1.18; MTL 0.57-0.63; PpH 0.12-0.14; PpL 0.45-0.49; SI 91-95; SL 0.65-0.72.

Comments.

Apart from the diagnostic appearance of the propodeal spiracle, the morphology of the minor worker is unremarkable compared with other Melophorus , and the habits of this species may be generalized. The major worker is unknown. No sequencing has been carried out on M. macroschismus , which is represented by a few minor workers only from localities in the eastern wheatbelt and eastern goldfields, Western Australia and from Wilgena Stn, SA (TERC). The only available ecological data comes from a label for a specimen collected near Warrachupin, WA, which was taken from a nest in salt infected remnant bushland.

Etymology.

Latinized Greek macros (Greek makros ‘long’) plus schismus (Greek schism ‘cleft’); adjective in the nominative singular.