Melophorus marmar 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 : 197-200

Melophorus marmar Heterick, Castalanelli & Shattuck sp. n.

Types.

Minor worker holotype (bottom ant) from 16 km E of Fred Spring, Curdimurka, South Australia, 2 October 1978, P.J. M. Greenslade, inside fence on veg., 1E [ANIC32-900054] (ANIC). Paratypes: major and minor worker on same pin and with same details as holotype (ANIC); major worker, media worker and minor worker from Davenport Springs, 40 km W of Maree, South Australia, 30 September 1978, P.J. M. Greenslade, near water, 38. 3 (BMNH); major worker, media worker and minor worker from c. 27 km S of William Creek, South Australia 29.05s × 136.31E, South Australia, 22 September 1972, J.E. Feehan, ANIC Ants Vial 16.59 (MCZ).

Other material examined.

Western Australia: Lake Austin (Heterick, B.E. [M287/M288/M289]), Lake Lefroy (Gordon, R.).

Diagnosis.

Melophorus marmar species can be placed in the M. biroi species-group on the basis of characters of the clypeus, propodeum, mandible and palps. Furthermore, this species can also be placed in the M. brevignathus species-complex. This species-complex has the following diagnostic characters: in full-face view the head capsules of the major, media and minor workers are square with small, flattened eyes (except in the media and minor workers of M. marmar , which have a large, convex eye [but the eye is flattened in the major worker]); in profile, the eyes are placed anteriad of the midline of head capsule; the anterior margin of the clypeus is distinctly sinuate, projecting anteromedially as a bluntly triangular extension or flattened dimple in major and media workers; the five-toothed mandible of all workers is very narrow, parallel and coarsely striate throughout its length (broader and more finely striate in most members of the M. fieldi and the M. biroi species-complexes); and the maxillary palps in all workers is short, barely attaining neck sclerite at their greatest extension and often only reaching the midpoint of venter of head capsule when the head is moderately inclined. The eye of Melophorus marmar is placed low on head capsule, its bottom third intersected by an imaginary horizontal line separating head capsule (excluding mandibles) into equal upper and lower sectors, thus separating it from M. quadratus . The species can be distinguished from M. brevignathus by the following: in full-face view, the head is straight or even weakly concave and the appressed setae on the first gastral tergite in all workers are longer and separated from the preceding and succeeding rows by ≥ 1 × their own length. The eyes of the minor and media workers large and convex, those of the major worker flat.

Minor worker description.

Head. Head square; posterior margin of head planar to weakly convex; frons shining with superficial shagreenation or microreticulation only; 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 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; frontal lobes straight in front of antennal insertion. Anteromedial clypeal margin straight, or broadly and evenly convex with or without a vestigial anteromarginal dimple; clypeal psammophore set at or just above anterior clypeal margin; palp formula 6,4. Five to six mandibular teeth in minor worker; mandibles narrow, mandibular blade truncate, internal and external margins parallel or nearly so; third mandibular tooth slightly 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 shining and mainly smooth, vestigial shagreenation most noticeable on humeri and mesopleuron; anterior mesosoma in profile smoothly rounded anteriad, mesonotum flattened and projecting marginally over pronotum and on same plane as propodeum; appearance of erect pronotal setae short, (i.e., longest erect setae shorter than length of eye) and unmodified, or erect pronotal setae absent; in profile, metanotal groove shallow, broadly V or U-shaped; propodeum shining and smooth or with superficial and almost invisible microsculpture; propodeum rounded or angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity about 1:1; erect propodeal setae always absent; appressed propodeal setulae short, separated by more than own length and inconspicuous; 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 tapered with blunt vertex; node shining and distinctly shagreenate-microreticulate. Gaster. Gaster shining with superficial microreticulation; pilosity of first gastral tergite consisting of well-spaced, erect and semi-erect setae interspersed with regularly placed appressed setae. General characters. Colour shining brown to black, antennae yellow to light brown, legs often dark medially and conspicuously paler near joints.

Major worker description.

Head. Head as for minor worker; posterior margin of head weakly concave; cuticle of frons shining and smooth except for piliferous pits; pilosity of frons a mixture of well-spaced, distinctly longer erect and semi-erect setae interspersed with shorter decumbent setae. Eye moderate (eye length 0.20-0.49 length of head capsule), or small, (eye length less than 0.2 × length of head capsule); in full-face view, eyes set at midpoint of head capsule; in profile, eye set anteriad of midline of head capsule; eyes elliptical. In full-face view, frontal carinae straight or weakly convex; frontal lobes straight in front of antennal insertion. Anterior clypeal margin weakly sinuate with anteromedial dimple; clypeal psammophore set below 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, but equivalent in length to remaining teeth; masticatory margin of mandibles approximately aligned vertically or weakly oblique. Mesosoma. Integument of pronotum, mesonotum and mesopleuron shining with very superficial microreticulation, entire lower mesopleuron distinctly shagreenate, or moderately shining and shagreenate throughout; anterior mesosoma in profile broadly convex; erect pronotal setae short, (i.e., shorter 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 1:1 and 1:2; erect propodeal setae present and abundant (at least a dozen), or present and sparse to moderate (1-12); appressed propodeal setae long, each reaching setae behind and in front, but not forming pubescence; 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 tapered with blunt vertex, or tapered with sharp vertex; node shining and distinctly microreticulate. Gaster. Gaster shining with superficial microreticulation; 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 shining brown, legs paler distally.

Measurements.

Worker (n = 4): CI 105-112; EI 16-18; EL 0.21-0.25; HL 1.09-1.40; HW 1.15-1.57; ML 1.21-1.56; MTL 0.88-1.13; PpH 0.13-0.16; PpL 0.49-0.60; SI 69-76; SL 0.88-1.09.

Comments.

In WA, Melophorus marmar was seen by the principal author nesting in Lake Austin (see Figs 3(d), 4) and collecting seeds, leaves and possibly carrion from the lake surrounds. On Lake Austin, the ant builds a cup-shaped mound of soil around the nest hole which is five or more centimetres above the dry lake surface, possibly as insurance against waterlogging. Some nests seen were more than forty metres from the edge of the Lake. This species also occurs in SA, and may be the Melophorus investigated by Schultheiss and his co-workers ( Schultheiss et al. 2012; Cheng et al. 2014), as part of a study on navigation in desert ants. Label data for three workers collected at Davenport Springs, 40 km W Marree indicate that they were collected 'near water’.

Etymology.

Old Irish marmar ( ‘marble’): after the shining appearance of the ant; adjective in the nominative singular.