Melophorus bruneus McAreavey

Heterick, Brian E., Castalanelli, Mark & Shattuck, Steve O., 2017, Revision of the ant genus Melophorus (Hymenoptera, Formicidae), ZooKeys 700, pp. 1-420 : 207-211

Melophorus bruneus McAreavey

Melophorus (Melophorus) brunea McAreavey 1949: 20, figs 57-65.

Types.

Holotype minor worker carded with paratype major worker and queen on top card, and paratype major worker and paratype minor worker of bottom card, all on same pin, also paratype major, minor and media workers and queens on two other pins, Nyngan New South Wales [ANIC] (examined: ANIC specimens ANIC32-05344).

Other material examined.

New South Wales: 25 km ENE Fort Gray Homestead (Morton, S.R.), 40 mi N Warren (Lowery, B.B.), Bogan River (Armstrong, J.), Callubri Station, 2 mi from homestead (Greaves, T.), CSIRO Lake Mere Field Station, near Louth (Bryannah, M. ), Fowlers Gap (Greenslade, P.J. M. ), Fowlers Gap (Greenslade, P.J. M. ), Kapunda, N Nyngan (Greenslade, P.J. M. ), Sturt National Park (Greenslade, P.J. M. ), Trundle (Lowery, B.B.). Queensland: ‘Gumbardo’ (Beutel, T.), ‘Merigol’ (Beutel, T.), 12 mi WSW Camel Creek Homestead, W Ingham (Dowse, J.E.), 22 mi E Condamine (Dowse, J.E.), 25 km SW Warwick (Greenslade, P.J. M. ), 40 km E Cameron Corner (Greenslade, P.J. M. ), 65 km E Birdsville (Forrest, J.), Eulo (Greenslade, P.J. M. ), Illaweena St. Drewvale (QM Party), Redlands Hilliards Ck, nr South St (RHC1) (QM Party), St. George (Lowery, B.B.). South Australia: 15 km NE Umberatana, Flinders Ranges (Greenslade, P.J. M. ), Eyre Hwy, 9.7 km NE Cootra (Heterick, B.E. [M324]), Lake Short Res. (Churchett, G. & R. [M87/M102]), Vokes Hill, Victoria Desert (Greenslade, P.J. M. ). Victoria: 15 km WNW Yaapeet (Andersen, A.N.), Sea Lake (Goudie). Western Australia: 12 km S of Exmouth (Heterick, B.E. [JDM32-001781]), 64 km E of Southern Cross (Heterick, B.E. [JDM32-001784]), Sandstone Rd turnoff (Heterick, B.E. [M295]), Tropicana Minesite (Summerhayes, J. [JDM32-004538]).

Diagnosis.

Melophorus bruneus can be placed in the M. biroi species-group on the basis of characters of the clypeus, propodeum, mandible and palps. The species is also placed in the M. fieldi species-complex because of the appearance of the anteriorly placed clypeal psammophore, the compact propodeum, the presence of more than one preapical spine on the metatibia, at least in the major worker, the long, even spindly legs and the unmodified mandible in the major worker. Melophorus bruneus workers require careful checking to distinguish them from related species, particularly those of M. turneri and M. fieldi . Most M. bruneus workers can be distinguished from all taxa except M. fieldi by the following combination of characters: (1) eye relatively large (eye length 0.50 × length of side of head capsule in minor worker, approximately 0.33 × length of side of head capsule in major worker ≥), (2) in full-face view, periphery of upper frons surrounded to about the level of the eyes with short, bristly, erect setae that are often flattened distally; (3) minor worker small (HW ≈ 0.56-0.59 mm); (4) non-iridescent head of major worker relatively smooth and gleaming (e.g., Fig. 54(a)) and, (5) clypeal psammophore of fine setae placed at or about midpoint of clypeus. The minor worker of Melophorus bruneus is distinguished from that of M. fieldi by its brown or dark reddish-brown but not blackish-brown colour that lacks a dull, silky sheen, by its smoothly convex pronotum when seen in profile, by the longer, often flexuous erect setae on the mesosoma (length of longer setae ≥ greatest width of antennal scape) and, in relatively glabrous minor workers, the long and conspicuously pale appressed setae on the mesosoma. The major worker has short, sometimes modified setae that are far more numerous than those of the major worker of M. fieldi and these give a shaggy appearance to most majors; moreover, the appressed setae on gaster are longer than in M. fieldi and overlap. Some populations of M. bruneus have glabrous minor workers. These can be distinguished from related species (particularly M. turneri and M. inconspicuus ) by their matt, microreticulate heads and the relatively long, pale, appressed setae on the gaster (similar species usually have erect setae on the mesosoma, they have smoother and more shining heads and they have short, appressed setae on the gaster).

Minor worker description.

Head. Head approximately oval with straight sides; posterior margin of head planar or weakly convex; frons matt or with weak sheen, microreticulate or microreticulate-shagreenate; pilosity of frons a mixture of a few well-spaced, erect setae interspersed with appressed setae only. Eye large (eye length ≥ 0.50 × 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 straight or weakly convex; frontal lobes curved toward antennal insertion. Anteromedial clypeal margin broadly and evenly convex; clypeal psammophore set at or above midpoint of clypeus; palp formula 6,4. Five to six mandibular teeth in minor worker; mandibles narrow, strap-like, internal and external margins parallel or nearly so; 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 microreticulate, microreticulation reduced on humeri, or with weak to moderate sheen and superficial microreticulation (more pronounced on mesopleuron); anterior mesosoma in profile broadly convex; appearance of erect pronotal setae short, (i.e., longest erect setae shorter than length of eye) and unmodified, or short and often expanded distally, at times clavate; 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 1:1 and 1:2; erect propodeal setae present and abundant (greater than 12); appressed propodeal setulae long and closely aligned, creating pubescence; propodeal spiracle situated nearer to midpoint of propodeum than to its declivitous face, and shorter (length <than 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 thick, appressed setae that form pubescence, interspersed with numerous short, bristly, erect setae. General characters. Colour brown, gaster (and often head) darker than mesosoma.

Major worker description.

Head. Head square; posterior margin of head planar or weakly convex; cuticle of frons matt or with weak sheen, indistinctly shagreenate; pilosity of frons a mixture of a few well-spaced, erect setae interspersed with appressed setae only. Eye moderate (eye length 0.20-0.49 length of head capsule); in full-face view, eyes set at about midpoint of head capsule; in profile, eye set anteriad of mid line 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 broadly convex with anteromedial dimple; clypeal psammophore set at or above midpoint of clypeus; palp formula 6,4. Five mandibular teeth in major worker; mandibles narrow, strap-like, internal and external borders parallel or nearly so; third mandibular tooth distinctly shorter than apical tooth and teeth numbers two and 4; masticatory margin of mandibles approximately aligned vertically or weakly oblique. Mesosoma. Integument of pronotum, mesonotum and mesopleuron matt with indistinct shagreenate sculpture throughout; anterior mesosoma in profile broadly convex; erect pronotal setae short, (i.e., shorter than length of eye) and unmodified, or short and often expanded distally, at times clavate; 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 1:1 and 1:2; erect propodeal setae present and abundant (at least a dozen); appressed propodeal setae long and separated by at least own length; propodeal spiracle situated at least twice its width from the declivitous face of propodeum, and shorter (length less than 0.50 × height of propodeum), or 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 tapered with blunt vertex; node shining and faintly shagreenate-microreticulate. Gaster. Gaster shining, shagreenate ('LP record’ appearance); pilosity of first gastral tergite consisting of well-spaced, erect and semi-erect setae interspersed with regularly spaced appressed setae. General characters. Colour of head and foreparts brownish-orange to brown with darker brown to blackish gaster.

Measurements.

Worker (n = 8): CI 103-127; EI 24-41; EL 0.24-0.37; HL 0.57-1.23; HW 0.59-1.55; ML 0.78-1.55; MTL 0.48-0.94; PpH 0.08-0.14; PpL 0.31-0.64; SI 64-108; SL 0.64-0.99.

Comments.

Major workers of Melophorus bruneus can be mistaken for the large-eyed major workers of some Melophorus turneri , so careful attention needs to be given to the circlet of short, stout setae on the vertex of the head capsule and the numerous, short, curved, erect setae on the head and mesosoma in the former. Most minor workers are distinctive with their vestiture of long, flexuous setae, but some populations in the NT and SA lack such setae. In these cases the matt, microreticulate nature of the frons and long appressed setae on the mesosoma are diagnostic, except for separation from M. fieldi . Minor and major workers of M. fieldi and M. bruneus can be separated based on different degrees of pilosity. While material has been available for sequencing, obtaining molecular data has proven difficult. The position of M. bruneus in the three-gene tree (Suppl. material 1) suggests a close relationship with M. fulvidus . However, this is counterindicated by evidence of likely hybridization with M. turneri (well-separated from M. bruneus on the three-gene tree). The evolutionary position of M. bruneus within the M. fieldi complex must therefore be considered uncertain.

This species is widely distributed in all mainland Australian states, but is more common in drier, inland areas. Pitfall traps have accounted for most specimens, but some have been hand-collected. Label data variously record savanna woodland, Callitris , mallee, scribbly gum and heath and 'pure Eucalyptus dum (osa)' habitat and there are two records of red soil. One specimen was collected in a parking bay. In all likelihood this a generalist scavenger of plant and animal matter like many other members of the M. fieldi complex. Minor workers collected by the principal author north of Wiluna, WA, in relatively cool conditions (for a Melophorus ) emerged timidly from a single, simple nest hole in red, lateritic soil with many surface ironstone pebbles. There is no other mention of the ecology of the ant from the labels, and neither is there any other information from McAreavey in his description of the taxon.