Melophorus canus 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 : 79-82

Melophorus canus Heterick, Castalanelli & Shattuck sp. n.

Types.

Holotype minor worker (top ant) from Goora Rock area, 70 miles from Esperance, Western Australia, 23 December 1969, B.B. Lowery, limestone mallee under rock [ANIC32-900003] (ANIC). Paratypes: 2 media workers, major worker and minor worker on same pin and with same details as the holotype (ANIC); 3 minor workers and major worker from Denmark, Western Australia, 19 December 1969, B.B. Lowery [ANIC32-900001] (BMNH); 2 minor workers, media worker, 3 major workers and male from Trundle, New South Wales, 9 January 1964, B.B. Lowery, in red soil, box pine scrub, Y35 [ANIC32-900005] (MCZ); minor worker from 107.2 km SSE of Newman 23°53'54"S, 120°36'14"E, Western Australia, October 1996, S. van Leeuwen & R. N. Bromilow, Invert., pitfall trap S3, Sand plain [JDM32-001987] (WAM).

Other material examined.

Queensland: ‘Merigol’ (Beutel, T.), Billabong W Salty Bore, Cravens Peak Station (Lemann, C. [ANIC32-035406]). South Australia: Black Oak Creek, Koonamore (Greenslade, P.J. M. [ANIC32-900004]). Western Australia: 0.9 km along Tanami Rd (Heterick, B.E. [M202]), Geraldton (Clark, J. [ANIC32-900002]), Mumbemarra Hill (10 km E of Geraldton) (Heterick, B.E. [JDM32-001986]).

Diagnosis.

Melophorus canus 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). This particular species is distinctive because the main teeth of the mandible are supplemented with small or indistinct denticles, the total number of teeth and denticles ≥ six. Also, in full-face view, the head of the minor worker is indented below the eye, giving a bell-shaped appearance to the head capsule. This latter character is shared only with M. griseus , which, however has the typical unmodified Melophorus mandible. The species has a very dull, shaggy appearance, the workers being matt, shagreenate, and with very many long, flexuous setae over silvery pubescence.

Minor worker description.

Head. Head approximately oval, sides of head divergent towards mandibular articulations; posterior margin of head strongly convex; frons matt or with weak sheen, microreticulate or microreticulate-shagreenate; pilosity of frons a mixture of many long, curved, semi-erect setae and decumbent and appressed setae of varying lengths that form a coarse pubescence. 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 straight or weakly convex, or straight, divergent posteriad; frontal lobes straight in front of antennal insertion, or curved inward in front of antennal insertion. Anteromedial clypeal margin narrowly protrusive anteromedially, the protrusion with a square border; clypeal psammophore set at or just above anterior clypeal margin; palp formula 6,4. Mandibular teeth in minor worker consisting of four distinct apical teeth with the basal denticle separated by one to several minute denticles or crenulations; 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, shagreenate on pronotum and dorsum of mesonotum, otherwise microreticulate; anterior mesosoma in profile broadly convex; appearance of erect pronotal setae long (i.e., longest erect setae longer than length of eye) and unmodified; in profile, metanotal groove shallow, broadly V or U-shaped; propodeum shining and shagreenate; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity between 3:2 and 4:3; erect propodeal setae present and abundant (greater than 12); appressed propodeal setulae long and closely aligned, creating pubescence; 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 distinctly shagreenate-microreticulate. Gaster. Gaster weakly shining with indistinct shagreenation; pilosity of first gastral tergite consisting of a mixture of curved, erect and semi-erect setae and decumbent and appressed setae that form a variable pubescence. General characters. Colour brown or black (concolorous or bicoloured).

Major worker description.

Head. Head quadrate (i.e., heart-shaped); posterior margin of head planar or weakly concave; cuticle of frons matt or with weak sheen, microreticulate; pilosity of frons a mixture of many long, curved, semi-erect setae over well-spaced short semi-erect, decumbent and appressed setae. 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, divergent posteriad; frontal lobes straight 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. Mandibular teeth in major worker consisting of four distinct apical teeth with the basal denticles separated by one to several minute denticles or crenulations; 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 pronotum smoothly rounded anteriad and flattened posteriad, mesonotum narrowly convex; erect pronotal setae long (i.e., longer than length of eye) and unmodified; in profile, metanotal groove shallow, broadly V- or U-shaped; propodeum matt or with a weak sheen and microreticulate; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity between 3:2 and 1:1; erect propodeal setae present and abundant (at least a dozen); appressed propodeal setae long and closely aligned, creating pubescence; propodeal spiracle situated nearer to midpoint of propodeum than to its declivitous face, and shorter (length less than 0.50 × height of propodeum), or situated at least twice its width from the declivitous face of propodeum, and shorter (length less than 0.50 × height of propodeum). Petiole. In profile, petiolar node squamiform; in full-face view, shape of petiolar node generally rounded with median indentation; node shining and faintly shagreenate-microreticulate. Gaster. Gaster weakly shining with indistinct shagreenation; pilosity of first gastral tergite consisting of a mixture of curved, erect and semi-erect setae and decumbent setae that form a variable pubescence. General characters. Colour dark reddish-brown.

Measurements.

Worker (n = 6): CI 87-111; EI 21-43; EL 0.31-0.41; HL 0.83-1.72; HW 0.72-1.91; ML 1.29-1.93; MTL 0.77-1.00; PpH 0.16-0.22; PpL 0.51-0.80; SI 57-137; SL 0.98-1.08.

Comments.

Melophorus canus is widely distributed throughout mainland Australia but is nowhere particularly common. The species is rendered distinctive by the long flexuous setae over thick, shining grey, appressed pilosity (hence the name), the somewhat bell-shaped appearance of the head of the minor worker when seen in full-face view and the appearance of the mandible. Genetic sequencing places it as the sister species to M. griseus . Collections have been made in a variety of habitats and geographic zones, and vegetation associations include limestone mallee and box-pine scrub but the habits of this species are unknown. A picture of the minor worker is found in fig. 15d in Greenslade 1979.

Etymology.

Latin canus ( ‘grey’ or ‘hoary’); adjective in nominative singular.