Melophorus attenuipes 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 : 77-79

Melophorus attenuipes Heterick, Castalanelli & Shattuck sp. n.

Types.

Holotype minor worker (bottom ant) from 1 km N Mulga Downs OC 22°19'33"S, 118°58'47"E, Western Australia, 24 May 2004-4 May 2005, CALM Pilbara Survey, Site RHNW05, ethylene glycerol pitfalls [JDM32-002000] (WAM). Paratypes: major worker, on same pin and with same details as holotype (WAM); minor worker, Zuytdorp 27°15'S, 114°04'E, Western Australia, 26 September-19 October 1994, A. Sampi/L. Cresswell, ZU4: Wet pits WAM/CALM survey Carnarvon Basin [JDM32-001998] (ANIC); minor worker, Zuytdorp 27°15'S, 114°04'E, Western Australia, 26 September-19 October 1994, A. Sampi/L. Cresswell, ZU4: Dry pits WAM/CALM survey Carnarvon Basin [JDM32-001999] (MCZ).

Diagnosis.

Melophorus attenuipes 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). The Minor worker of this species is characterised as being very small (HW ≤ 0.50 mm), but it is the metafemur of the minor worker that is the best diagnostic charcter. This body part is attenuated to the midpoint and thereafter is of uniform width until its junction with the tibia (the media worker has a similar metafemur, but the attenuation is more gradual and less conspicuous). The head of the minor worker rather elongate and very strongly domed. The major worker can best be identified by the flattened anteromedial sector of its clypeus, this sector not extending beyond the lateral flanks of the clypeus.

Minor worker description.

Head. Head approximately oval with straight sides; posterior margin of head strongly convex; frons matt or with weak sheen, microreticulate or microreticulate-shagreenate; frons consisting exclusively or almost exclusively of well-spaced, appressed setae only (small, erect setae, if present, usually confined to ocu lar 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; eyes elliptical or slightly reniform. In full-face view, frontal carinae distinctly concave; frontal lobes curved toward 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 and superficial microreticulation (more pronounced on mesopleuron); anterior mesosoma in profile smoothly rounded anteriad, thereafter pronotum and whole of mesonotum flattened and on same plane as propodeum; erect pronotal setae absent; in profile, metanotal groove shallow, indicated mainly by an angle; propodeum shining and shagreenate; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity between 1:1 and 1:2; 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 with vestigial sculpture. 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 of head and foreparts tan, gaster chocolate, coxae and femora brown, tibia and tarsi mainly depigmented yellowish.

Major worker description.

Head. Head quadrate (i.e., heart-shaped); posterior margin of head weakly convex; cuticle of frons matt or with weak sheen, microreticulate; 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 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. In full-face view, frontal carinae straight, convergent posteriad; frontal lobes curved inward in front of antennal insertion. Anterior clypeal margin narrowly convex and protruding anteromedially, clypeal margin entire or weakly indented; 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 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; erect pronotal setae absent; in profile, metanotal groove deep, V-shaped; propodeum matt or with a weak sheen and microreticulate; propodeum smoothly rounded or with indistinct angle; propodeal dorsum and declivity confluent; erect propodeal setae absent; appressed propodeal setae 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). Petiole. In profile, petiolar node squamiform; in full-face view, shape of petiolar node tapered with squared-off vertex; node matt, shagreenate. Gaster. Gaster shining, shagreenate ('LP record’ appearance); pilosity of first gastral tergite consisting of well-spaced short, inconspicuous, appressed setae, erect setae (present in at least some workers) confined to margin of sclerite. General characters. Colour of foreparts and legs orange tan (head slightly more reddish), gaster chocolate.

Measurements.

Worker (n = 3): CI 80-114; EI 20-32; EL 0.15-0.31; HL 0.56-1.37; HW 0.45-1.57; ML 0.74-1.69; MTL 0.53-1.10; PpH 0.09-0.18; PpL 0.42-0.72; SI 79-156; SL 0.70-1.24.

Comments.

The minor worker of this small species is recognizable by virtue of its small size (HW ≤ 0.50mm), much attenuated and long hind femur and strongly domed vertex. The media and major workers are less easily characterized, but the major worker has a flattened clypeus. The species appears to be restricted to the mid-west and Pilbara regions of Western Australia, and is known from a couple of collections only (WAM, one TERC record). Nothing is known of its biology or its genetics.

Etymology.

Compound of Latin ad ( ‘towards’) plus tenuis ( ‘thin’) and Greek pes (pl. of pous ‘foot’); adjective in nominative singular.