Melophorus turbineus 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 : 193-195

Melophorus turbineus Heterick, Castalanelli & Shattuck sp. n.

Types.

Holotype minor worker (bottom ant) from Gawler Ranges, South Australia, 4 October 1972, P.J. M. Greenslade, (5), 4/10 (5), M. sp. 8 (ANIC32- 066636) (ANIC). Paratypes: Minor worker on same pin and with same details as holotype (damaged after photograph taken) (ANIC); minor worker from Gawler Ranges, Western Australia, 4 October 1972, P.J. M. Greenslade, (5) [ANIC-900100] (MCZ).

Diagnosis.

Melophorus turbineus 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). Next to M. minimus , M. turbineus is probably the smallest Melophorus . The minor worker has a distinctive propodeum that is produced vertically and is conical in profile. The propodeal spiracle is very large, being approximately 0.75 × height of propodeum. The eye is also large (eye length approximately 0.40 × length of side of head capsule). These characteristics make this species readily recognisable. The major worker is unknown.

Minor worker description.

Head. Head approximately oval with straight sides; posterior margin of head weakly convex, or planar or weakly convex; frons shining and smooth except for piliferous pits; 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 at about midpoint of head capsule; in profile, eye set around midline of head capsule; roughly ovoid, eye narrowed posteriad. In full-face view, frontal carinae distinctly concave; frontal lobes curved inward in front of antennal insertion. Anteromedial clypeal margin straight and retroussé anteromedially; clypeal psammophore set at or just above anterior clypeal margin; palp formula 6,4. Five mandibular teeth in minor worker to seven; 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 shining and smooth on dorsum, entire lower mesopleuron distinctly striolate-microreticulate; anterior mesosoma in profile pronotum smoothly rounded anteriad and flattened posteriad, mesonotum narrowly convex; erect pronotal setae absent; in profile, metanotal groove shallow, broadly V or U-shaped; propodeum shining, with multiple hair like striolae; propodeum sharply conical; length ratio of propodeal dorsum to its declivity not applicable, propodeal dorsum reduced to a narrow sliver; erect propodeal setae always absent; appressed propodeal setulae sparse or absent, if present then not regularly spaced; 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 smooth throughout. Gaster. Gaster smooth and glossy; pilosity of first gastral tergite consisting of well-spaced short, inconspicuous, appressed setae only, erect setae always absent. General characters. Colour of head and gaster chocolate, mesosoma tan.

Measurements.

Worker (n = 2): CI 98-100; EI 33-35; EL 0.13-0.14; HL 0.37-0.43; HW 0.36-0.43; ML 0.53-0.54; MTL 0.24-0.28; PpH 0.06-0.07; PpL 0.18-0.21; SI 88-96; SL 0.35-0.38.

Comments.

Minor workers of this tiny species are recognizable because of their roundly conical propodeum when seen in profile, and their large propodeal spiracle. Like other members of their clade, they have a scalloped mesopleuron. No sequencing work has been done on the taxon. The major worker is unknown and the minor worker material is confined to two pins of ants collected in the Gawler Ranges, SA. There are no accompanying collection data (apart from the fact that the worker on one pin would have been pitfall-trapped by Greenslade) and nothing more is known of this ant.

Etymology.

Latin turbineus ( ‘conical’); adjective in nominative case.