Melophorus wheeleri

Within its range, this is a common species in arid and semi-arid areas.

Identification
Heterick et al. (2017) - Melophorus wheeleri can be placed in the Melophoprus biroi species-group on the basis of characters of the clypeus, propodeum, mandible and palps. The species is also placed in the Melophoprus wheeleri species-complex because it agrees with the following apomorphies possessed by the complex: the minor worker often has more than five teeth, the largest major worker has a short, massive, elbowed mandible directed posteriad; in profile, the maxillary palps are short in the major and generally short in minor workers (in the minor worker, usually only attaining the neck sclerite at their maximum extent when the head is moderately inclined) and, in full-face view, the anterior margin of the clypeus in the large major worker is usually planar or weakly concave (variable in other subcastes but planar or narrowly protuberant anterior clypeal margins predominate). Melophorus wheeleri shares only with Melophorus diversus the following combination of apomorphies: the anterior sector of the clypeus of minor worker is strongly folded back towards the mandible, and the clypeal psammophore is placed on a distinct ledge that may be carinate, the minor worker mandible has 5-9 teeth and denticles, the head, mesosoma and gaster of all workers have short, inconspicuous appressed setae that are usually separated by more than their own length (if more elongate, as in some small minor workers, then the ant is glossy and weakly sculptured) and the media and major workers are quite large Melophorus (HW of the large major worker ≥ 2.60 mm).

Most workers of Melophorus wheeleri can be distinguished from M. diversus workers in having the head of minor worker always with some sculpture, the head being matt to moderately shining in appearance, erect setae are almost always lacking on the pronotum and the first gastral tergite, and the eye of the minor worker is usually less than 0.30× length of side of head capsule. The major worker is similar to the major worker of M. diversus but either has a glabrous mesosoma or possesses short, bristly setae on the mesosoma and is commonly matt in appearance (WA, NT) but may be glossy (eastern states). (In M. diversus the head of the minor worker is smooth with just vestigial sculpture [the head often glossy], erect non-marginal setae are always present on the first gastral tergite with one or two small erect setae also present on the pronotum of some individuals, the eye of the minor worker is large [0.30× length of side of head capsule] and the major worker usually has many fine, erect setae on the mesosoma [though these may be more sparse and bristly in a few individuals]). However, the distinctions between these two species are not always observed and a few individuals, possibly hybrids, may be unable to be placed in either taxon with confidence.

The ant can be identified and separated from near relatives by the glabrous first gastral tergite and smaller eye in the minor worker (less than 0.30× length of side of head capsule), features of the clypeus and body sculpture and the massive mandible of the major worker.

Differentiation between M. diversus and M. wheeleri is very difficult in some cases. All M. wheeleri sequenced belong to the more distinctive western form with its dark or even blackish-crimson colouring, and these specimens form a uniform cluster in the five-gene tree as a sister taxon to several other M. wheeleri complex species. In the three-gene tree, this species is sister to Melophorus marmar. Unfortunately, the eastern form, which has a bright red or orange head in the major worker, was not represented in the sequencing.

Melophorus omniparens (=M. wheeleri), the type specimens of which come from Queensland, represents the glossy light-coloured form of the taxon. The two media workers syntypes seen have a sharply-defined edge to the anterior clypeal margin, which contrasts with the blunter, more carinate margin seen in the syntype workers of Melophorus wheeleri. Those latter workers, from Tennant Creek, NT, represent the darker, more matt western form of the ant. In the absence of evidence to the contrary (which may or may not come from sequencing of the eastern morphotype), these differences are here regarded as part of the intraspecific variation seen in the species, since the conformation of the clypeus is very variable across the broad range of the ant.

Distribution
Heterick et al. (2017) - Specimens from the ANIC Collection come from NT, QLD, SA and WA but this taxon seems to be replaced by Melophorus diversus in NSW. In WA (Heterick 2009) M. wheeleri is found from the Pilbara down to the gold fields, and into the wheatbelt at least as far west as Kellerberrin.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Biology
Heterick et al. (2017) - This extremely common Melophorus of arid and semi-arid areas can often be identified from its large nests, which typically are littered with small pebbles and plant remnants such as seed husks and stems. The species is ostensibly granivorous (Andersen, 2007), and workers are often seen transporting small seeds back to their nests. Workers have been recorded carrying seeds of Lepidium phlebopetalum (Brassicaciae) at Jigalong Station, WA (Heterick, 2009). Despite their ubiquity, label data for these ants are scanty, but they are able to tolerate disturbance; specimens have been collected from a golf course at Meekatharra, WA.

Nomenclature

 *  wheeleri. Melophorus wheeleri Forel, 1910b: 60 (s.w.m.) AUSTRALIA.
 * Viehmeyer, 1914b: 43 (q.).
 * Combination in M. (Erimelophorus): Wheeler, W.M. 1935c: 71.
 * Status as species: Viehmeyer, 1914b: 43; Forel, 1915b: 88; Emery, 1925b: 12; Taylor & Brown, 1985: 125; Bolton, 1995b: 250; Heterick, 2009: 98; Heterick, et al. 2017: 368 (redescription).
 * Senior synonym of omniparens: Heterick, et al. 2017: 368.
 * omniparens. Melophorus omniparens Forel, 1915b: 85 (w.) AUSTRALIA.
 * Combination in M. (Erimelophorus): Wheeler, W.M. 1935c: 71.
 * Status as species: Emery, 1925b: 12; Taylor & Brown, 1985: 124; Bolton, 1995b: 250.
 * Junior synonym of wheeleri: Heterick, et al. 2017: 368.

Worker
Heterick et al. (2017) - (n = 8): CI 106-125; EI 11-31; EL 0.28-0.40; HL 0.69-2.85; HW 0.74-3.57; ML 0.87-2.54; MTL 0.55-1.49; PpH 0.09-0.30; PpL 0.35-1.11; SI 42-83; SL 0.61-1.51.

Minor. Head. Head square; posterior margin of head planar or weakly 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 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, or elongate. In full-face view, frontal carinae straight, divergent posteriad; frontal lobes straight in front of antennal insertion. Anteromedial clypeal margin straight, or broadly and evenly convex; clypeal psammophore set below midpoint of clypeus, or set at or just above anterior clypeal margin; palp formula 6,4. Five mandibular teeth in minor worker to nine; mandibles triangular, weakly incurved; third mandibular tooth may be separated from tooth no. 3 and tooth no. 4 by one or more intercalary teeth, size appears to vary; 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; erect pronotal setae absent; in profile, metanotal groove shallow, broadly V- or U-shaped; propodeum shining and finely striolate and microreticulate; propodeum smoothly rounded or with indistinct angle, or angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity about 1:1, or not applicable, 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), or 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 uniformly rounded; node shining and smooth with vestigial sculpture, or shining and distinctly shagreenate-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 reddish-brown with black gaster to concolorous blackish-brown.

Major. Head. Head quadrate (i.e., heart-shaped); posterior margin of head strongly concave; cuticle of frons shining and smooth except for piliferous pits, or shining with superficial shagreenation or microreticulation only, or matt or with weak sheen, microreticulate; 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 head capsule); in full-face view, eyes set at about 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 toward antennal insertion. Anterior clypeal margin broadly emarginate; clypeal psammophore set at or above midpoint of clypeus; palp formula 6,4. Four mandibular teeth in major worker-5; mandibles strongly incurved, apical sector weakly carinate or incompletely carinate; third mandibular tooth distinctly shorter than apical tooth and teeth numbers two and four; masticatory margin of mandibles medially indented. Mesosoma. Integument of pronotum, mesonotum and mesopleuron shining with indistinct microsculpture that is most pronounced on lower surfaces; anterior mesosoma in profile broadly convex; erect pronotal setae short and unmodified, or weakly expanded distally; in profile, metanotal groove shallow, broadly V- or U-shaped; propodeum shining, with multiple hair like striolae; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity between1:1 and 1:2; erect propodeal setae variable in number, may be 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 generally rounded with median indentation, or tapered with squared-off 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 foreparts variably dark crimson or blackish-red (western form) to orange tan or vermillion (eastern form); gaster always dark brown to blackish-brown.

Type Material
Heterick et al. (2017) - Syntype (probable) major and minor workers Tennants [sic] Creek, Northern Territory [,, ] (examined: ANIC specimens ANIC32-053440, AntWeb images of BMNH specimen BMNH(E)1016285, CASENT0903262 and MHNG specimens CASENT0909826, CASENT0909827). Also seen: three pins (1 × dealated queen, male and badly damaged minor (gaster, node and legs only), 1 × winged queen and two media workers and 1 × major, media and minor worker), Tennant Creek, Northern Territory. All three pins carry co-type labels and locality labels that appear to be written by another hand, and the syntype status of these nine specimens is thus brought into question.