Melophorus sulconotus 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 : 115-117

Melophorus sulconotus Heterick, Castalanelli & Shattuck sp. n.

Types.

Holotype minor worker (middle ant), Kapalga, Alligator Rivers area, Northern Territory, 7-9 September 1993, P.J. M. Greenslade, 8Aii traps, [ANIC32-900071] (ANIC). Paratypes: 2 minor workers on same pin and with same data as holotype (ANIC).

Other material examined.

Western Australia: 4 km E Lake Argyle (Heterick, B.E. [M219]).

Diagnosis.

Melophorus sulconotus is a member of the M. 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 M. 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). In M. sulconotus the tibiae possess fine, appressed pubescence in addition to stout, socketed, appressed to subdecumbent setae No major worker was available for examination. The chief diagnostic feature in the minor worker is the flattened posterior pronotum and mesonotum which descends steeply to the metanotal groove. This species is restricted to the wetter Northern Kimberley distinct and the far north Northern Territory.

Minor worker description.

Head. Head square; posterior margin of head weakly convex; frons matt or with weak sheen, microreticulate or microreticulate-shagreenate; frons consisting of appressed pubescence, with many short, unmodified, erect setae. Eye small (eye length less than 0.2 × 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 or weakly convex; frontal lobes straight, elevated. Anteromedial clypeal margin broadly and evenly convex and protrusive; 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 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; appearance of erect pronotal setae short, (i.e., longest erect setae shorter than length of eye) and unmodified; in profile, metanotal groove deep, ‘V’ -shaped; propodeum matt or with a weak sheen and microreticulate; propodeum always smoothly rounded; propodeal dorsum and declivity confluent; erect propodeal setae present and abundant (greater than 12); appressed propodeal setulae minute and closely aligned, creating a silvery sheen; propodeal spiracle situated at least twice its width from the 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 smooth with vestigial sculpture. Gaster. Gaster shining, shagreenate ('LP record’ appearance); pilosity of first gastral tergite consisting of thick, appressed setae that form pubescence, interspersed with numerous short, bristly, erect setae. General characters. Colour of foreparts orange, legs light tan, gaster dark brown.

Measurements.

Worker (n = 2): CI 97-99; EI 19-20; EL 0.27-0.29; HL 1.38-1.55; HW 1.34-1.53; ML 2.24-2.46; MTL 1.47-1.58; PpH 0.22-0.26; PpL 0.86-0.93; SI 120-127; SL 1.71-1.84.

Comments.

This rare and rather attractive Torresian species in the M. aeneovirens species-group is known only from the minor and media workers. The profile is distinctive (noted under ‘Comments’ for Melophorus rufoniger ). Genetic sequencing indicates the ant may be sister to M. rufoniger . Specimens collected from the Victoria Hwy roadside near Kununurra, Western Australia, decorated their nest with flattened pebbles much larger than the ants.

Etymology.

Latin sulcus ( ‘groove’) plus Neo-Latin notus ( ‘back’); adjective in the nominative singular.