Melophorus quadratus 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 : 200-202

Melophorus quadratus Heterick, Castalanelli & Shattuck sp. n.

Types.

Holotype minor worker (bottom ant) from c. 9 km E of Finke, Northern Territory, 30 September 1972, J.E. Feehan, ANIC Ants Vial 15.155 [ANIC32-900053]. Paratypes: Major worker on same pin and with same details as holotype (damaged) (ANIC); 3 minor workers from Birthday Hill, N. Tarcoola, 3 October 1976, P.J. M. Greenslade, (2) (ANIC); 2 major workers from 5 km E Kingoonya 30.55S, 135.23E, South Australia, 30 September 1981, D. Davidson/S. Morton, 59a (BMNH); 3 minor workers from Mt Davies turnoff, Victoria Desert, South Australia, 8 October 1976, P.J. M. Greenslade, (2) [ANIC32-900183] (MCZ). major worker and minor worker from Vokes Hill, Victoria Desert, South Australia, 8 October 1976, P.J.M Greenslade (6)a (SAM).

Other material examined.

South Australia: 3 km W Emu Camp, Victoria Desert (Greenslade, P.J. M. ), Emu Camp, Victoria Desert (Greenslade, P.J. M. ), Lake Meramangye, Victoria Desert (Greenslade, P.J. M. ).

Diagnosis.

Melophorus quadratus 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. Unlike M. brevignathus and M. marmar , M. quadratus has the eye, in full-face view, placed very high on capsule, and slightly above an imaginary horizontal line separating the head capsule (excluding mandibles) into equal upper and lower sectors; moreover the workers are glabrous (erect mesosomal setae are present in the other two species in the complex).

Minor worker description.

Head. Head square, or quadrate (i.e., heart-shaped); posterior margin of head planar or weakly concave, or strongly concave; 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 ocular triangle or posterior margin of head). Eye small (eye length less than 0.2 × 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, divergent posteriad; frontal lobes straight in front of antennal insertion. Anteromedial clypeal margin broadly emarginate with projecting anteromedial dimple; clypeal psammophore set at or above midpoint of clypeus; palp formula 6,4. Five mandibular teeth in minor worker; mandibles narrow, mandibular blade truncate, 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 with weak to moderate sheen and superficial microreticulation (more pronounced on mesopleuron); anterior mesosoma in profile broadly convex; erect pronotal setae absent; in profile, metanotal groove shallow, indicated mainly by an angle; propodeum shining and microreticulate; propodeum smoothly rounded or with indistinct angle; propodeal dorsum and declivity confluent; erect propodeal setae always absent; appressed propodeal setulae short, separated by more than own length and inconspicuous; 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 tapered with blunt vertex; node shining and distinctly microreticulate. 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 blackish-brown.

Major worker description.

Head. Head as for minor worker; posterior margin of head weakly concave; cuticle of frons shining with superficial shagreenation or microreticulation only; 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). Eyes small, (eye length less than 0.2 × 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 straight, divergent posteriad; frontal lobes curved inward in front of antennal insertion. Anterior clypeal margin sinuate, weakly projecting anteromedially; clypeal psammophore set at or above midpoint of clypeus; palp formula 6,4. Five mandibular teeth in major worker; mandibles narrow, mandibular blade truncate, 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 aligned vertically 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; erect pronotal setae absent; in profile, metanotal groove shallow, broadly V- or U-shaped; propodeum shining and microreticulate; propodeum always smoothly rounded; propodeal dorsum and declivity confluent; erect propodeal setae absent; appressed propodeal setae short, separated by more than own length and inconspicuous; propodeal spiracle 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 uniformly rounded; node shining and smooth with vestigial microreticulation anteriad. 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 the sclerite. General characters. Colour blackish-brown.

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.

Workers of Melophorus quadratus are distinguished from those of the preceding two species by the high position of the eyes on the head capsule; workers are also glabrous. The species has been collected from remote localities in the Victoria Desert and from Tarcoola, SA, with one record from the Finke River, NT. Nothing more is known about this ant.

Etymology.

Latin quadratus ( ‘square’); adjective in the nominative singular.