Melophorus vitreus 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 : 277-279

Melophorus vitreus Heterick, Castalanelli & Shattuck sp. n.

Types.

Holotype minor worker (top ant) from Black Swan Mine 30°28'S, 121°43'E, Western Australia, 11 December 2003-5 January 2004, P. Langlands/J. Osborne, site data C4,8 [JDM32-004585] (WAM). Paratypes: 3 minor workers on same pin and with same details as holotype (WAM); 4 minor workers from Kunoth Paddock near Alice Springs, Northern Territory, 3-6 February 1975, P.J. M. Greenslade, Trap VM, 20) [ANIC32-900122] (ANIC); minor worker from 15 km SE of Alice Springs 23.51S, 133.58E, Northern Territory, 9 October 1991, D. Davidson/S. Morton, 120C (BMNH); 2 minor workers from 17 km S of Rabbit Flat, Northern Territory, 19 May 1986, P.J. M. Greenslade, (8) B, 11) (MCZ); minor worker from Mt Whaleback, Newman, Western Australia, July 1984, K. J. Walker [JDM32-004586] (QM).

Other material examined.

Queensland: ‘Gumbardo’ (Beutel, T.), ‘Merigol’ (Beutel, T.). Western Australia: 1 km W Canna (Heterick, B.E. [M322]).

Diagnosis.

Melophorus vitreus can be placed in the M. biroi species-group on the basis of characters of the clypeus, propodeum, mandible and palps. The species is also placed in the M. fieldi species-complex because of the appearance of the anteriorly placed clypeal psammophore, the compact propodeum, the presence of more than one preapical spine on the metatibia, at least in the major worker, the long, even spindly legs and the unmodified mandible in the major worker. In profile, the minor worker of M. vitreus is gracile, with a short, thick petiolar node terminating in a smoothly rounded vertex, the clypeus is rounded and somewhat protuberant the eye very large (eye length ≥ 0.50 × length of side of head capsule) and the cuticle is extremely glossy with the mesopleuron completely smooth or with only a very superficial microreticulate pattern. The combination of the very large eye, the protuberant clypeus, the smooth mesopleuron and the general glossiness will serve to identify the ant. Most specimens exhibit the " pillipes ' condition. The major worker is unknown.

Minor worker description.

Head. Head square; posterior margin of head weakly convex; frons shining and smooth except for piliferous pits; pilosity of frons a mixture of a few well-spaced, erect setae interspersed with appressed setae only. Eye large (eye length ≥ 0.50 × length of side of head capsule); in full-face view, eye set at about midpoint of head capsule; in profile, eye set anteriad of head capsule; eyes elliptical or slightly reniform. In full-face view, frontal carinae distinctly concave; frontal lobes straight in front of antennal insertion. Anteromedial clypeal margin broadly and evenly convex; clypeal psammophore set at or above midpoint of clypeus; palp formula 6,4. Five mandibular teeth in minor worker; mandibles triangular, weakly incurved; third mandibular tooth distinctly shorter than apical tooth and teeth numbers two and four; masticatory margin of mandibles approximately vertical or weakly oblique. Mesosoma. Integument of pronotum, mesonotum and mesopleuron shining and mainly smooth, vestigial shagreenation most noticeable on humeri and mesopleuron; anterior mesosoma in profile weakly elevated anteriad, thereafter gently sinuate, pronotum and mesonotum on same plane; appearance of erect pronotal setae short, (i.e., longest erect setae shorter than length of eye) and unmodified, or erect pronotal setae absent; in profile, metanotal groove shallow, broadly V or U-shaped; propodeum shining and smooth or with superficial and almost invisible microsculpture; propodeum always smoothly rounded; propodeal dorsum and declivity confluent; erect propodeal setae variable in number, may be absent; appressed propodeal setulae short, separated by more than own length and inconspicuous; propodeal spiracle situated on or beside declivitous face of propodeum, and shorter (length <0.50 × height of propodeum). Petiole. In profile, petiolar node subcuboidal, vertex bluntly rounded; in full-face view, shape of petiolar node uniformly rounded; node shining and smooth throughout. Gaster. Gaster smooth and glossy; pilosity of first gastral tergite consisting of well-spaced, erect and semi-erect setae interspersed with regularly placed appressed setae. General characters. Colour of foreparts orange tan to reddish brown, gaster brown to blackish-brown.

Measurements.

Worker (n = 6): CI 99-106; EI 36-41; EL 0.23-0.25; HL 0.56-0.66; HW 0.56-0.70; ML 0.81-0.96; MTL 0.45-0.52; PpH 0.08-0.107; PpL 0.30-0.36; SI 96-105; SL 0.59-0.67.

Comments.

This small ant resembles a smooth, glossy, gracile M. turneri , but can be distinguished from that species by features of the clypeus, the eye and the node and by its glossy, gracile mesosoma. Most specimens seen exhibit the ' pillipes ' condition, but a few workers lack these fine setae. The species is definitely known from NT and WA but, based on its habitat preference, it may also be looked for in SA. Sequencing data places it near M. incisus and M. ankylochaetes . Limited ecological data indicate it has been collected in mallee and also on lateritic sandplain with an overlay of proteaceous heathland and small trees.

Etymology.

Latin vitreus ('of glass’ or 'resembling glass’); adjective in the nominative singular.