Melophorus platyceps

This is quintessentially an ant of the southern mallee woodlands. Label data are minimal, as is so often the case with this genus. The species is depicted in Greenslade 1979, Fig. 15a. Greenslade suggested the ant may be adapted to foraging under bark, and this species was among the most common Melophorus species taken in a recent collection by University of Western Australia researchers using bee-intercept traps on the base of eucalypts in the Avon Wheatbelt district. (Heterick et al. 2017)

Identification
Heterick et al. (2017) - Melophorus platyceps is a member of the Melophorus aeneovirens species-group (in full-face view, the anterior clypeal margin convex, apron-like and covering whole or part of the retracted mandible, except in Melophorus nemophilus, the medial clypeal sector often produced so that it is protrusive when seen in profile; the psammophore frequently with coarse and well-separated ammochaetae, these always placed on or just above anterior margin; in profile, the propodeum elongate and oblique or broadly rounded), and the M. aeneovirens species-complex (in full-face view, psammophore ranged along or just above anterior margin of clypeus and following the curve of the margin; anterior margin of clypeus broadly medially produced, and often with central notch that may be deeply impressed, but is never acuminate at its midpoint; metatibia with maximum of two rows of preapical spines). Melophorus platyceps has a very flattened head, but can be separated from several other flat-headed Melophorus by its short maxillary palps which don’t reach the neck, and, in particular, in its more-or-less linear mesosomal dorsum after a weak anterior pronotal incline (when seen in profile). These two features, in particular, distinguish it from the otherwise similar Melophorus tenuis, which belongs to the same species-complex. The metanotal groove is vestigial in the minor worker and weakly impressed in media and major workers, and the anterior clypeal margin weakly convex.

This species is unlikely to be mistaken for any other Melophorus because of its combination of an elongate, flattened head, flattened trunk and short palps.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Biology
On the three-gene tree this species is sister to M. praesens. (Heterick et al. 2017)

Nomenclature

 *  platyceps. Melophorus platyceps Heterick, Castalanelli & Shattuck, 2017: 114, fig. 17 (w.) AUSTRALIA.

Worker
(n = 4): CI 84-115; EI 19-33; EL 0.20-0.29; HL 0.73-1.30; HW 0.62-1.50; ML 1.21-1.83; MTL 0.68-0.98; PpH 0.11-0.21; PpL 0.51-0.72; SI 77-156; SL 0.96-1.16.

Minor. Head. Head rectangular; posterior margin of head weakly convex; frons coriaceous; 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. In full-face view, frontal carinae straight, divergent posteriad; 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 and teeth numbers two and four; masticatory margin of mandibles approximately vertical or weakly oblique. Mesosoma. Integument of pronotum, mesonotum and mesopleuron matt with indistinct shagreenate sculpture throughout; anterior mesosoma in profile weakly elevated anteriad, thereafter uniformly more-or-less flat with metanotal suture absent or vestigial; erect pronotal setae absent; in profile, metanotal groove a weak or vestigial furrow; propodeum matt or with weak sheen and finely striolate; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity about 2:1; erect propodeal setae always 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 squamiform; in full-face view, shape of petiolar node square with rounded angles; node weakly shining and faintly striolate. Gaster. Gaster shining, shagreenate (‘LP record’ appearance); pilosity of first gastral tergite consisting of wellspaced short, inconspicuous, appressed setae only, erect setae always absent. General characters. Colour of foreparts orange or orange tan, gaster dark brown.

Major. Head. Head square; posterior margin of head planar or weakly concave; cuticle of frons matt or with weak sheen, indistinctly 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 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. In full-face view, frontal carinae straight, divergent posteriad; frontal lobes straight in front of antennal insertion. Anterior clypeal margin broadly and evenly convex; clypeal psammophore set below midpoint of clypeus; palp formula 6,4. Five mandibular teeth in major worker; mandibles triangular, weakly incurved; third mandibular tooth distinctly shorter than apical tooth and teeth numbers two and four; masticatory margin of mandibles approximately aligned vertically or weakly oblique. Mesosoma. Integument of pronotum, mesonotum and mesopleuron with weak to moderate sheen, shagreenate on pronotum and dorsum of mesonotum, otherwise microreticulate; anterior mesosoma in profile convex anteriad, mesonotum overlapping pronotum, planar or slightly sinuate posteriad; erect pronotal setae short, (i.e., shorter than length of eye) and unmodified, or erect pronotal setae absent; in profile, metanotal groove shallow, indicated mainly by an angle and metathoracic spiracles; propodeum matt or with weak sheen and microreticulate-striolate; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity about 4:3; erect propodeal setae absent; appressed propodeal setae short, separated by more than own length and inconspicuous; propodeal spiracle situated on or beside declivitous face of propodeum, and shorter (length less than 0.50 × height of propodeum). Petiole. In profile, petiolar node squamiform; in full-face view, shape of petiolar node square with rounded angles; node shining and faintly shagreenate-microreticulate. Gaster. Gaster shining, shagreenate (‘LP record’ appearance); pilosity of first gastral tergite consisting of well-spaced short, inconspicuous, appressed setae, erect setae (present in at least some workers) confined to margin of the sclerite. General characters. Colour as for minor worker.

Type Material
Holotype minor worker (top ant) from Koonamore, South Australia, 24 February 1973, P.J.M. Greenslade, (2) [ANIC32-900117]. Paratypes: 2 major workers on same pin and with same details as holotype ; 3 minor workers from 31.3 km S of Shearer’s Quarters 141°01'40"S, 34°50'30"E, Millewa South Bore Track, Murray Sunset National Park, Victoria, 14-23 November 2002, C. Lambkin, D. Yeates, N. Starwick & J. Recsei, 2m Sharkey malaise opening in closed mallee [ANIC32-043294] (ANIC); 2 major workers and minor worker from Blyth, N of Adelaide, South Australia, 11 June 1957, B.B. Lowery, 50 ft, mallee scrub, ANIC Ants Vial 22.69 ; major and 2 minor workers from Blyth, N of Adelaide, South Australia, 28 November 1957, B.B. Lowery, mallee scrub, ANIC Ants Vial 22.68 ; 3 minor workers from 5 km NW Ketchowla HS, South Australia, 23 January 1975, P.J.M. Greenslade, (5) ; minor worker 2 km N of Wongan Hills, Western Australia, 24 February 1989, B. Heterick, soil, native vegetation, rural environment, 505, 8 MelBH35.

Etymology
Compound of Greek platys (‘broad’, ‘flat’) plus Latin -ceps (‘-headed’ [from caput]); adjective in the nominative singular.