Melophorus barbellulatus 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 : 325-327

Melophorus barbellulatus Heterick, Castalanelli & Shattuck sp. n.

Types.

Holotype media worker (middle ant on top rectangle) from Tardun, Western Australia, 24 May 1963, C. Mercer, Melophorus [ANIC32-900080]. Paratypes: 2 major workers, alate queen and 2 males on two rectangles on same pin with same details as holotype (ANIC); minor worker from Boddington, Western Australia, 1983, A.C. Postle, Worsley FAFS III WOR 103, 'Name: Melophorus fulvihirtus , ID: Heterick, B.E., Date: 6 December 2001' [sic] [Note: this ant is closely related to M. fulvihirtus but is not that species-BEH] [JDM32-001976] (WAM).

Other material examined.

South Australia: 14 km Keilira Stn (Hirst, D. [M110]).

Diagnosis.

Melophorus barbellulatus is one of only two members of the M. fulvihirtus species-group, both identified by having the head and mesosoma extensively covered with short, stout, peg-like bristles and, in outline, the pronotum and mesonotum flattened. The metatibial apical spur is stout but very short. This species is distinguished from its sister species by having the short peg-like setae much reduced on the antennal scape and absent from the legs, and the cuticle is finely shagreenate and weakly shining (matt and coriaceous in M. fulvihirtus ). The posterior posterior margin of head of major and minor workers is planar, and the mandible of the minor worker is coarsely striate.

Minor worker description.

Head. Head square; posterior margin of head planar or weakly concave; frons matt or with weak sheen, microreticulate or microreticulate-shagreenate; frons consisting of very short, erect, spinous setae with closely aligned, very minute, appressed setae that create a faint silvery sheen. Eye moderate (eye length 0.20 -0.49 length of side of head capsule); in full-face view, eye 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 concave; frontal lobes curved inward in front of antennal insertion. Anteromedial clypeal margin broadly and evenly convex; clypeal psammophore set at or just above anterior clypeal margin; palp formula 6,4. Five to six mandibular teeth in minor worker; mandibles triangular, weakly incurved; third mandibular tooth distinctly shorter than apical tooth, but equivalent in length to remaining teeth; 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; erect pronotal setae absent; in profile, metanotal groove a weak or vestigial furrow; propodeum matt or with a weak sheen and indistinctly shagreenate; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity about 1:1; erect propodeal setae present and abundant (greater than 12); appressed propodeal setulae minute and closely aligned, creating a silvery sheen; 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 matt with indistinct microsculpture. Gaster. Gaster weakly shining with indistinct shagreenation; pilosity of first gastral tergite consisting of thick, appressed setae that form pubescence, interspersed with numerous short, bristly, erect setae. General characters. Colour tan with areas of brown infuscation.

Major worker description.

Head. Head square; posterior margin of head planar or weakly concave; cuticle of frons matt or with weak sheen, microreticulate; frons consisting of very short, erect, spinous setae with closely aligned, very minute, appressed setae creating a faint silvery sheen. Eye moderate (eye length 0.20-0.49 length of head capsule); in full-face view, midpoint of head capsule; in profile, eye set anteriad of midline of head capsule; eyes elliptical. In full-face view, frontal carinae concave; frontal lobes curved toward antennal insertion. Anterior clypeal margin convex, acuminate anteromedially, margin entire; 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 weakly shining and coriaceous; anterior mesosoma in profile steeply rounded anteriad, thereafter pronotum and whole of mesonotum flattened and on a higher plane than propodeum; erect pronotal setae absent; in profile, metanotal groove shallow, indicated mainly by an angle and metathoracic spiracles; propodeum matt or with a weak sheen and microreticulate; propodeum distinctly angulate, propodeal angle sharp; length ratio of propodeal dorsum to its declivity greater than 1:2; erect propodeal setae present and abundant (at least a dozen); appressed propodeal setae minute and closely aligned, creating a silvery sheen; propodeal spiracle situated on or beside 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 matt, and microreticulate. Gaster. Gaster weakly shining with indistinct shagreenation; pilosity of first gastral tergite consisting of well-spaced, short, thick, erect setae interspersed with minute, appressed setae. General characters. Colour of foreparts orange, gaster brown.

Measurements.

Worker (n = 3): CI 99-114; EI 20-28; EL 0.18-0.27; HL 0.62-1.31; HW 0.62-1.31; ML 0.79-1.48; MTL 0.45-0.76; PpH 0.10-0.13; PpL 0.36-0.69; SI 71-109; SL 0.68-0.93.

Comments.

Melophorus barbellulatus has been found in South Australia (SAMA, TERC), Victoria (TERC) and WA (WAM, TERC) but is nowhere common. The nature of the trunk and the short, peg-like setae align it with M. fulvihirtus , but sequencing of one specimen was unsuccessful, for reasons that are uncertain. The ant is rendered distinctive by reason of details of the sculpture, mandible and vertex of the head (see species-group key). No ecological or other data are available from labels, and it is unknown whether this species is an ant raider like its relative.

Etymology.

Latin dim. of barbella ('short, stiff hair’) plus -atus ('of the nature of’) referring to the tiny, short, stiff setae on the body; noun in the nominative singular standing in apposition to the generic name.