Melophorus incisus 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 : 228-230

Melophorus incisus Heterick, Castalanelli & Shattuck sp. n.

Types.

Holotype minor worker (bottom ant) from 5 km SE of Anthony’s Lagoon 18.00S, 135.34E, Northern Territory, 14 October 1981, D. Davidson & S. Morton, 167b [ANIC32-900170] (ANIC). Paratypes: 2 minor workers on same pin and with same details as holotype (ANIC); major worker from Argyle Diamonds via Kununurra, July 1991, Site 23 Melophorus sp. 15, Postle, A.T. [JDM32-001996] (ANIC); minor and major worker from 5 km SE of Anthony’s Lagoon 18.00S, 135.34E, Northern Territory, 14 October 1981, D. Davidson & S. Morton, 167a [ANIC32-900170], V, K, 6 (BMNH); 2 media and a minor worker from 22 km SE of Katherine, Northern Territory, 8 April 1978, P.J. M. Greenslade, (7), 14 [ANIC32-900090] (MCZ); minor worker from Marandoo minesite 22°38'11"S, 118°07'31"E, Western Australia, 28 August-18 September 2009, J.L. Brown, pitfall trap RR1 0M, mine dump [JDM32-004528] (WAM).

Other material examined.

Western Australia: 30 km N Sandfire Hill (Heterick, B.E. [M184/M185/M186]), Pannawonica (Boisduval, M. [JDM32-004620]), Port Hedland (Weatherill, L.), Port Hedland (Heterick, B.E. [M270]), Sandford Rock (Yandle, S. [JDM32-001991]).

Diagnosis.

Melophorus incisus 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. Furthermore, this species clusters with several others in the M. fieldi complex which share the following characters: gaster with curved erect setae, semi-erect setae and a few decumbent setae only, genuine appressed setae lacking; the body generally strongly sculptured and hirsute and the antennal scapes and legs with whorls of many fine, straight setae. Melophorus incisus can then be distinguished from closely allied forms by its globose mesonotum and propodeum and the fact that the mesonotum, the mesopleuron and the propodeum are separated from each other by a deep sulcus.

Minor worker description.

Head. Head approximately oval with straight sides; posterior margin of head strongly convex; frons shining and smooth except for piliferous pits, or matt or with weak sheen, microreticulate or microreticulate-shagreenate; pilosity of frons a mixture of short, erect and semi-erect setae interspersed with shorter decumbent setae and well-spaced, short, appressed setae. 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, convergent posteriad; frontal lobes curved inward in front of antennal insertion. Anteromedial clypeal margin broadly convex with anteromedial dimple; clypeal psammophore set at or above midpoint of clypeus; palp formula 6,4. Five mandibular teeth in minor worker; mandi bles triangular, weakly incurved; 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 matt or with weak sheen and microreticulate throughout, or pronotum smooth and shining, mesonotum shining and superficially microreticulate, mesopleuron densely microreticulate and may be almost matt; anterior mesosoma in profile broadly convex; appearance of erect pronotal setae long (i.e., longest erect setae longer than length of eye) and unmodified; in profile, metanotal groove a narrow but deep slit; propodeum shining and densely microreticulate, with distinct striolae on metapleuron; propodeum always smoothly rounded; length ratio of propodeal dorsum to its declivity not applicable, propodeal dorsum reduced to a narrow sliver; erect propodeal setae present and abundant (greater than 12); appressed propodeal setulae sparse or absent, if present then not regularly spaced 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 subcuboidal, vertex bluntly rounded; in full-face view, shape of petiolar node uniformly rounded; node shining and smooth throughout, or shining and striolate. Gaster. Gaster smooth and glossy; pilosity of first gastral tergite consisting wholly or mainly of long, curved setae, appressed setae apparently absent. General characters. Colour of foreparts reddish-brown to chocolate, gaster chocolate.

Major worker description.

Head. Head square; posterior margin of head strongly convex; cuticle of frons shining and smooth except for piliferous pits and a few striolae around antennal insertions and frontal carinae; 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); 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 concave; frontal lobes curved inward 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 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 shining with very superficial microreticulation, entire lower mesopleuron distinctly shagreenate; anterior mesosoma in profile broadly convex; erect pronotal setae long (i.e., longer than length of eye) and unmodified; in profile, metanotal groove deep, V-shaped; propodeum shining and microreticulate; propodeum always smoothly rounded; propodeal dorsum and declivity confluent; erect propodeal setae present and abundant (at least a dozen); appressed propodeal setae sparse or absent, if present then not regularly spaced; propodeal spiracle situated on or beside declivitous face of propodeum, and longer (length ≥ 0.50 × height of propodeum). In profile, petiolar node squamiform; in full-face view, shape of petiolar node tapered with squared-off vertex; node shining and smooth throughout. Gaster. Gaster shining with superficial micro reticulation; pilosity of first gastral tergite consisting wholly or mainly of long, curved setae, appressed setae apparently absent. General characters. Colour of foreparts orange tan, gaster brown.

Measurements.

Worker (n = 6): CI 96-117; EI 19-31; EL 0.18-0.29; HL 0.60-1.27; HW 0.78-1.49; ML 0.84-1.55; MTL 0.48-0.93; PpH 0.13-0.20; PpL 0.36-0.59; SI 70-118; SL 0.68-1.05.

Comments.

A small, hairy species, Melophorus incisus is easily recognized by the deeply incised grooves on the mesosoma, and the rotund nature of the anterior thoracic segments and the propodeum. This ant resembles M. ankylochaetes , and genetic sequencing confirms a sister relationship between the two taxa. The species occupies a wide range in the NT and WA, but has not been recorded from any other state thus far. Foragers have been aspirated on the crest of a small dune 30 km from Sandfire Hill, WA and from among tussock grass in seaside dunes in the town of Port Hedland, WA, but other data are lacking.

Etymology.

Latin incisus ( ‘cut’ or ‘dissected’); adjective in the nominative case.