Melophorus longiceps 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 : 175-177

Melophorus longiceps Heterick, Castalanelli & Shattuck sp. n.

Types.

Holotype minor worker from CSIRO Lake Mere field stn near Louth, New South Wales, paddock B, January 1995, M. Bryannah, paddock D (EXC) Interc[ept], Melophorus sp. K [ANIC32-900104] (ANIC). Paratypes: 2 minor workers from CSIRO Lake Mere field stn near Louth, New South Wales, paddock B, January 1995, M. Bryannah, paddock E Runoff, ' Melophorus sp. K’ [ANIC32-066665] (BMNH); major worker from CSIRO Lake Mere field stn near Louth, New South Wales, paddock B, January 1995, M. Bryannah, paddock G Runoff, ' Melophorus sp. K’ [ANIC32-066665] (MCZ).

Diagnosis.

Melophorus longiceps can be placed in the M. biroi species-group on the basis of characters of the clypeus, propodeum, mandible and palps. The species is placed in the M. biroi species-complex on the basis of a further suite of characters (viz, metatibia of major worker with only one preapical spur [except rarely in the mjobergi clade]; clypeal psammophore placed anteriorly at or just above anterior margin of clypeus in the minor worker and often in the major worker; head dorsoventrally compressed to varying degrees in the minor worker of most species with the eyes placed high on the sides; compact legs, and small body size [excluding mjobergi clade] HW of smallest minor 0.36 mm, average HW of smallest minors 0.46 mm; HW of largest known major 1.29 mm, average HW of largest majors [where known] 1.05 mm). In profile, the head of the minor worker is distinctly dorsoventrally flattened and, in full-face view, extremely narrow (CI ≤ 75). This extreme narrowness is a unique character that defines this species. Some M. biroi have rather narrow heads, but in those cases the CI is> 85. The major worker is unknown.

Minor worker description.

Head. Head rectangular; posterior margin of head planar or weakly concave; frons matt or with weak sheen, 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. 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 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 with weak to moderate sheen, shagreenate on pronotum and dorsum of mesonotum, otherwise microreticulate; anterior mesosoma in profile weakly elevated anteriad, thereafter gently sinuate, pronotum and mesonotum on same plane; erect pronotal setae absent; in profile, metanotal groove shallow, indicated mainly by an angle; propodeum matt or with a weak sheen and microreticulate; propodeum angulate, propodeal angle blunt, or distinctly angulate, propodeal angle sharp; length ratio of propodeal dorsum to its declivity about 1:1; 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 uniformly rounded; node shining and distinctly microreticulate. Gaster. Gaster shining, shagreenate ('LP record’ appearance); pilosity of first gastral tergite consisting of well-spaced short, inconspicuous, appressed setae only, erect setae always absent. General characters. Colour uniformly chocolate with some tan highlights.

Measurements.

Worker (n = 2): CI 76-81; EI 30-38; EL 0.15-0.16; HL 0.56-0.63; HW 0.43-0.51; ML 0.72-0.82; MTL 0.41-0.43; PpH 0.07-0.10; PpL 0.29-0.34; SI 111-121; SL 0.52-0.56.

Comments.

Currently, Melophorus longiceps , known only from the minor worker, has been recorded from the Lake Mere Field Station, near Louth, NSW. However, workers morphologically similar to this species were seen in the TERC Collection but time did not permit a detailed examination. This material came from WA (Ningbing Ra) and NT (Kalkarindji, Humbert River and Pigeon Hole Stn) and included a major worker. The different biogeography, however, precludes a too ready association of the two sets of taxa. The elongate, flattened head of this species separates it from the rest of the genus, but in other respects it is identical to M. biroi (in which the head capsule varies in length). A worker was collected from a paddock, but there are no other ecological data, and no specimens were available for sequencing.

Etymology.

Latin longus ( ‘long’) plus -ceps ( ‘-headed’ [from caput]); adjective in the nominative singular.