Melophorus brevignathus 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 : 195-197

Melophorus brevignathus Heterick, Castalanelli & Shattuck sp. n.

Types.

Holotype minor worker (bottom ant) from Saint George [sic], Queensland, 15 January 1965, B.B. Lowery, sav. Woodland, ANIC Ants Vial 20.216 [ANIC32-900055] (ANIC). Paratypes: 2 major workers on same pin and with same details as holotype (ANIC); 2 minor workers from Kunoth Paddock, Northern Territory on separate pin but with exactly the same details but lacking small label ‘10’ (BMNH); 2 media workers and a minor worker from Kunoth Paddock, near Alice Springs, Northern Territory, 26 October 1974, P.J. M. Greenslade, (12), 10 (MCZ); 2 major workers and a minor worker from 75 km W of Sandringham HS, Queensland, 6 June 1980, P.J. M. Greenslade, (5), 20) (QM).

Other material examined.

Northern Territory: Kunoth Paddock, near Alice Springs (Greenslade, P.J. M. ). Queensland: St. George (Lowery, B.B.).

Diagnosis.

Melophorus brevignathus 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 an teromedially 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 brevignathus 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. marmar by the following: in full-face view, the head is distinctly convex and the appressed setae on the first gastral tergite in all workers are shorter and separated from the preceding and succeeding rows by at least 2 × their own length. The eyes of the minor worker are similar to those of major worker.

Minor worker description.

Head. Head square; posterior margin of head weakly concave; 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). 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, divergent posteriad; frontal lobes straight in front of antennal insertion. Anteromedial clypeal margin sinuate with anteromedial dimple; clypeal psammophore set below midpoint of clypeus; palp formula 6,4. Mandibular teeth in minor worker four to five; mandibles narrow, mandibular blade truncate, internal and external margins parallel or nearly so; third mandibular tooth distinctly shorter than apical tooth and tooth no. two, tooth no. four vestigial; masticatory margin of mandibles approximately vertical or weakly oblique. Mesosoma. Integument of pronotum, mesonotum and mesopleuron moderately shining and shagreenate throughout; 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 erect pronotal setae absent; in profile, metanotal groove shallow, broadly V or U-shaped; propodeum shining and microreticulate; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity between 1:1 and 1:2; 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 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 of foreparts brown to dark brown, gaster 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, ap pressed setae only (small, erect setae, if present, usually confined to ocular triangle or posterior margin of head). 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 straight, divergent posteriad; frontal lobes straight in front of antennal insertion, or curved inward in front of antennal insertion. Anterior clypeal margin sinuate with anteromedial dimple; clypeal psammophore set below midpoint of clypeus; palp formula 6,4. Mandibular teeth in major worker 4-5; mandibles narrow, mandibular blade truncate, internal and external margins 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 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 finely striolate and microreticulate; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity between 1:1 and 1:2; erect propodeal setae absent; appressed propodeal setae short, separated by more than own length and inconspicuous; 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 uniformly rounded, or tapered with blunt vertex; node shining and distinctly microreticulate. Gaster. Gaster shining with superficial microreticulation; pilosity of first gastral tergite consisting of well-spaced, erect and semi-erect setae interspersed with regularly spaced appressed setae, or consisting of short, bristly, erect setae over well-spaced, short, appressed setae. General characters. Colour of foreparts reddish-brown or brown, gaster blackish-brown.

Measurements.

Worker (n = 6): CI 109-112; EI 16-23; EL 0.21-0.26; HL 0.84-1.44; HW 0.92-1.62; ML 1.00-1.56; MTL 0.67-1.02; PpH 0.12-0.18; PpL 0.41-0.63; SI 66-84; SL 0.77-1.06.

Comments.

Melophorus brevignathus is distinguished from Melophorus quadratus by the position of the eye towards the middle of the head capsule, and from Melophorus marmar by other details of the head capsule, the size of the eyes in the minor worker and the appearance of the setae on the first gastral tergite. This species has been collected in box pine scrub over red soil and in savanna woodland in QLD and it also occurs in the NT. The species has not been sequenced and no other details are known.

Etymology.

Latin brevis ( ‘short’) plus Neo-Latin gnathus ( ‘jaw’); adjective in the nominative singular.