Melophorus teretinotus 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 : 119-121

Melophorus teretinotus Heterick, Castalanelli & Shattuck sp. n.

Types.

Holotype minor worker (top ant) from Ethel Creek, Western Australia, February 1996, F. K. Sengarayar [JDM32-004552] (WAM). Paratypes: minor worker on same pin and with same data as holotype (WAM); minor worker from Barrow Island, 20°47'38'S, 115°36'24"E, Western Australia, 24 April, 2005, S. Callan, Suction RI pit AL [JDM32-004553] (ANIC).

Other material examined.

Western Australia: Argyle Diamond Mine via Kununurra (Postle, A. [JDM32-004554]), Barrow Island (N. Gunawardene/C. Taylor [M314]).

Diagnosis.

Melophorus teretinotus 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. teretinotus the tibiae possess stout, socketed, appressed to subdecumbent setae only, with fine, appressed pubescence lacking. The minor worker only is known. Melophorus teretinotus cannot be mistaken for any other Melophorus : the mesosoma is strongly arched, smooth and glabrous, the mesonotum and propodeum are confluent and the metanotal groove is completely lacking.

Minor worker description.

Head. Head square; posterior margin of head extended posteriad as a convex, sloping surface with a slight medioccipital protuberance; frons shining with superficial shagreenation or microreticulation only; 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 concave; frontal lobes curved inward in front of antennal insertion. Anteromedial clypeal margin narrowly convex and protruding, clypeal midpoint distinctly notched; 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; erect pronotal setae absent; in profile, metanotal groove absent; propodeum shining and uniformly striolate; propodeum always smoothly rounded; propodeal dorsum and declivity confluent; 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 smooth throughout. 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 brown, gaster slightly darker than foreparts.

Measurements.

Worker (n = 4): CI 82-85; EI 26-30; EL 0.21-0.25; HL 0.83-1.16; HW 0.68-0.98; ML 1.38-1.64; MTL 0.62-0.79; PpH 0.10-0.17; PpL 0.68-1.04; SI 127-149; SL 1.02-1.25.

Comments.

The odd outline of the minor worker of this species makes it impossible to confuse it with any other Melophorus . The absence of the metanotal groove is distinctive, and the shining, broadly expansive pronotum and mesonotum smoothed over into a deeply declivitous propodeum brings to one’s mind the curve of a snail shell. Only the minor worker has so far been recognized. All records have come from WA, where it appears occasionally in collections from the Kimberley and Pilbara region on the mainland and from Barrow Island, but the species is also likely to occur in the NT. The ecology of this ant is not known. Attempts to sequence its DNA have achieved only limited success with only the wingless gene successfully amplifying. Its closest relation is M. praesens , based on pairwise divergence of the Wg gene (1.8% pairwise divergence).

Etymology.

Latin terete ('cylindrical and tapering’) plus Neo-Latin notus ( ‘back’); adjective in the nominative singular.