Melophorus major Forel Status novus

Heterick, Brian E., Castalanelli, Mark & Shattuck, Steve O., 2017, Revision of the ant genus Melophorus (Hymenoptera, Formicidae), ZooKeys 700, pp. 1-420 : 244-246

Melophorus major Forel Status novus

Melophorus fieldi var. major Forel 1915: 87.

Types.

Syntype major worker and minor workers: major and minor worker on separate pins, Kimberley district, Western Australia [MHNG]. Also examined: MHNG, MSNG, NHRS AntWeb images of specimens (MHNG specimens CASENT0909812, CASENT0909813, MSNG specimen CASENT0905126, NHRS specimen NHRS-HEVA00003949).

Other material examined.

New South Wales: Moree (I. Oliver). Western Australia: 11 km N Wiluna (Davidson, D. & Morton, S.), 11 km N Wiluna (Davidson, D. & Morton, S. [ANIC32-066606]), 11 km N Wiluna (Davidson, D. & Morton, S. [ANIC32-066608]).

Diagnosis.

Melophorus major 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. The large-eyed Melophorus major closely resembles several related Melophorus , most obviously M. bruneus , M. fieldi and the M. turneri candidus form of M. turneri . The one distinctive feature that places at least the M. major minor worker apart from other Melophorus in its species-complex is the low placement of the clypeal psammophore: in profile, this structure is to be found just behind the anterior clypeal margin and it is also placed well below the midpoint of the clypeus in some major workers. At present the few known major workers cannot be separated with any confidence from related species or populations of species with an anteriorly situated psammophore, but the propodeum is narrow with an oblique dorsal face and the colour of major workers seen is shining brown with the gaster slightly darker, and this character may be helpful in some cases.

Minor worker description.

Head. Head square; posterior margin of head planar or weakly convex; frons shining with superficial shagreenation or microreticulation only; 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), or moderate (eye length 0.20-0.49 length of side of head capsule); in full-face view, eyes set at about 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 moderately shining and shagreenate throughout; anterior mesosoma in profile broadly convex; appearance of erect pronotal setae short, (i.e., longest erect setae shorter than length of eye) and unmodified; in profile, metanotal groove shallow, broadly V or U-shaped; propodeum shining and finely striolate and microreticulate; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity greater than 2:1; 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 longer (length ≥ 0.50 × height of propodeum), or 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 shagreenate-microreticulate. Gaster. Gaster shining, shagreenate ('LP record’ appearance); 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 brown, gaster blackish-brown.

Major worker description.

Head. Head square; posterior margin of head weakly concave; cuticle of frons shining with superficial shagreenation or microreticulation only; pilosity of frons a mixture of a few well-spaced, erect setae interspersed with appressed setae only. Eye moderate (eye length 0.20-0.49 length of head capsule); in full-face view, eyes set at about 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 at or just above anterior clypeal margin; 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 moderately shining and shagreenate throughout; anterior mesosoma in profile broadly convex; erect pronotal setae short, (i.e., shorter than length of eye) and unmodified; in profile, metanotal groove shallow, indicated mainly by an angle and metathoracic spiracles; propodeum shining and shagreenate; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity between 1:1 and1:2, or greater than 1:2; erect propodeal setae present and abundant (at least a dozen); appressed propodeal setae long and separated by at least own length; propodeal spiracle situated on or beside declivitous face of propodeum, 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 faintly shagreenate-microreticulate. Gaster. Gaster shining with superficial microreticulation; pilosity of first gastral tergite consisting of well-spaced, erect and semi-erect setae interspersed with regularly spaced appressed setae. General characters. Colour of foreparts orange tan, gaster blackish-brown.

Measurements.

Worker (n = 2): CI 99-112; EI 23-37; EL 0.28-0.37; HL 0.76-1.45; HW 0.75-1.63; ML 1.07-1.71; MTL 0.69-1.08; PpH 0.12-0.16; PpL 0.43-0.71; SI 70-109; SL 0.82-1.14.

Comments.

Apart from the low placement of the clypeal psammophore, this medium-sized Melophorus is completely unremarkable and can easily be mistaken for Melophorus inconspicuus or a dark M. hirsutipes , to which it is likely closely related. Only a handful of pinned workers from Wiluna, WA, and one pin of two minor workers from Moree, NSW, were available for analysis. However, ants of similar appearance have regularly turned up in some collections made in the Pilbara region of WA, as part of a survey by large mining companies, and the species may not be uncommon. However, no specimens have been available for sequencing. Because of the difficulty in separating this species (especially major workers) from several morphologically very similar taxa, its range is uncertain but it is likely to occur sparsely in drier areas across the continent in suitable habitat. No ecological data are available.

The name ‘major’ is given new species level status in this revision. The syntypes for this species (two separate pins available for specimen analysis and three Automontage photographs on AntWeb) reveal a few small differences from the remaining material; namely, the eye in the non-type material (both major and minor workers) is larger and the erect pilosity is longer and a little more extensive. These differences may be explained by biogeography, the type specimens having been collected in the Kimberley (not shown on the map because of the vagueness of the collection locality), and the others much further south. The media worker available for inspection, however, has the same protuberant clypeus and anteriorly placed clypeal psammophore seen in the non-type minor workers. This feature is distinctive and is not seen in any other member of the M. fieldi complex. The major worker does not always share this feature and is difficult to separate from allied species. The dark colouration and short propodeum with an oblique dorsal face (compared with an often blocky, square propodeum in similar species) help in the identification of major workers, but minor workers are needed for identifications to be definitive.