Melophorus inconspicuus

Despite its ubiquity, there are no data on the habits of this species (which, in any case, would not be identifiable in ecological papers) apart from the terse ‘ground forager’ found on a couple of labels, but it seems safe to assume it is a general scavenger of small carrion and vegetative matter. (Heterick et al. 2017)

Identification
Melophorus inconpicuus 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 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. Melophorus inconspicuus belongs to a clade of very similar and highly derived Melophorus that are also common and widespread, and specimens have to be checked carefully using the following characters before they can be distinguished from Melophorus bruneus, Melophorus fieldi, Melophorus hirsutipes, Melophorus longipes, Melophorus lanuginosus and Melophorus turneri: the eye in minor workers is moderate in size (large in M. bruneus and M. fieldi minor wokers), in profile, the clypeus is evenly convex or weakly concave in its anterior third, the petiolar node is thin, much less than 0.7× as wide as high and either straight or weakly bent posteriad. The appressed setae on the mesosoma and gaster are moderate in length and interspersed with bristly erect setae (this is a good character by which to distinguish this ant from workers of Melophorus turneri, in which the appressed setae are very short), the silvery pubescence is limited to small areas of the pronotum or entirely absent (forms a thick thatch in M. lanuginosus); the erect setae on mesosoma are generally few and bristly in appearance (often < diameter of eye, unlike the longer and more flexuous setae in M. hirsutipes) and the entire mesosoma may be glabrous. The cuticle is generally weakly shagreenate, except for the mesopleuron, and the foreparts are commonly moderately shining. the petiolar node in the minor worker essentially squamiform, that of major worker a true scale. The major worker can be distinguished from major workers of M. bruneus and M. fieldi by its larger size (HW > 1.70 mm versus HW < 1.60 mm) and its less finely sculptured and shinier appearance. The ‘pillipes’ condition (whorls of fine, erect setae on appendages) is always absent.

The name for this species seems apt, as this dull, nondescript member of the M. fieldi complex is better defined by what it isn’t than by unique diagnostic characters. In fact, the taxonomy of this ant is unsatisfactory, and more than one species may be lumped under the diagnostic features contained in the key and the description. In appearance, what is here called inconspicuus most closely resembles a blackish to medium brownish cross between hairier near relatives (M. hirsutipes and M. lanuginosus) and the glabrous or near glabrous M. turneri. Workers range from glabrous to ants with scattered, short pilosity. The appressed setae are longer than in M. turneri (separated from one another on the first gastral segment by less than their length or actually overlapping) and the head and mesosoma are matt or weakly shining with shagreenate sculpture, never strongly shining. The eye is smallish to moderate in size in all subcastes. Seen in full-face view, minor, media and major workers always have a few short, stout, unmodified setae on the vertex and these may encircle the vertex to about eye level as in M. bruneus and M. fieldi. However, the relatively smaller eye (EI 18-37 compared with an EI of 24-41 in M. bruneus and 26-42 in M. fieldi) in most specimens and the longer antennal scape will enable this ant to be distinguished from those taxa. The ‘pillipes’ condition has not been seen in this species, and it lacks the thatch of silvery appressed setae seen in M. lanuginosus. In a five-gene tree summary, M. inconspicuus is sister to M. hirsutipes, though this is based on just a single specimen of the typical form.

Distribution
This ant has a wide distribution throughout mainland Australia. Most samples have been collected in SA and southwestern WA.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Habitat
Heterick et al. (2017) - This species does not seem to have any preferred habitat The vegetation zones from which the species has been recorded are very diverse: Banksia woodland, dry sclerophyll, Casuarina, mallee woodland, Eucalyptus largiflorens, heath, mallee, savanna woodland, box-pine scrub, and ‘arid woodland’. Cambrai (SA) foragers were collected in dunes, while other samples have been taken near rivers, from clay pans and from red sand. At Hilarys, WA, the principal author has collected the blackish south-western form of this species in white beach sand at a car park about 150 m from the ocean. This form has a small eye. Black workers with similar features (held in ANIC) have been recorded from the Stirling RA, WA.

Nomenclature

 *  inconspicuus. Melophorus inconspicuus Heterick, Castalanelli & Shattuck, 2017: 262, fig. 60 (w.) AUSTRALIA.

Worker
(n = 8): CI 96–125; EI 18–37; EL 0.21–0.31; HL 0.59–1.38; HW 0.57–1.72; ML 0.86–1.68; MTL 0.58–1.05; PpH 0.08–0.19; PpL 0.35–0.71; SI 67–135; SL 0.76–1.15.

Minor. Head. Head square; posterior margin of head planar or weakly convex; frons matt or with weak sheen, microreticulate or microreticulate-shagreenate; pilosity of frons a mixture of a few well-spaced, erect setae interspersed with appressed setae only, or 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 or weakly convex; frontal lobes straight in front of antennal insertion. Anteromedial clypeal margin broadly emarginate with projecting anteromedial dimple, or straight; clypeal psammophore set at or above midpoint of clypeus; palp formula 6,4. Five mandibular teeth in minor worker; mandibles 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 with weak to moderate sheen, shagreenate on pronotum and dorsum of mesonotum, otherwise microreticulate; 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 matt or with a weak sheen and microreticulate; propodeum smoothly rounded or with indistinct angle; propodeal dorsum and declivity confluent; erect propodeal setae variable in number, may be absent; appressed propodeal setulae long, each reaching setae behind and in front, but not forming pubescence; propodeal spiracle situated on or beside declivitous face of propodeum, and longer (length ≥ 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 thick, appressed setae that form pubescence, interspersed with numerous short, bristly, erect setae. General characters. Colour concolorous brown to blackish-brown.

Major. Head. Head horizontally rectangular, broader than wide; posterior margin of head planar or weakly concave; cuticle of frons shining with superficial shagreenation or microreticulation only, or matt or with weak sheen, microreticulate; 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 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. In full-face view, frontal carinae straight, divergent posteriad; frontal lobes straight 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 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 present and abundant (at least a dozen); 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 uniformly rounded, or tapered with blunt vertex; node shining and faintly shagreenate-microreticulate. Gaster. Gaster shining, shagreenate (‘LP record’ appearance); pilosity of first gastral tergite consisting of short, bristly, erect setae over well-spaced, short, appressed setae. General characters. Colour of foreparts variably orange tan to chocolate, gaster chocolate.

Type Material
Holotype minor worker (bottom ant) from Mt Gason, South Australia, January-February 1995 (collector not stated); 546, ANIC ANTS VIAL 75.63 [ANIC32-006700]. Paratypes: Major and media worker on the same pin and with the details as the holotype (ANIC); 3 major workers from 10 km E of Mt Ive HS, Gawler Range, South Australia, 22 October 1980, P.J.M. Greenslade, B Se [ANIC32-066426] ; 2 major workers and minor worker from Banff, Coorong, South Australia, 13 October 1975, P.J.M. Greenslade, (3) [ANIC32-066405] (BMNH); 2 major workers and minor worker from Tomago 32°52'S, 151°45'E, New South Wales, 17 December 1992, G.P. Jackson, mined 1963 [ANIC32-015278] ; 1 major, 1 media and minor worker from Rocky River, Kangaroo Island, South Australia, [‘PT/’] 3 January 1977, P.J.M. Greenslade, ; 2 media workers and minor worker from Whitfords Beach 31°47'S, 115°43'E, Western Australia, 2 July 2005, B.E. Heterick, car park verge beside dune, mid pm [JDM32-001790] ; major worker and 2 media workers from Stirling Range Gold Holes, Western Australia, 28 October 1969, R.W.T, c 250m, dry sclero., R.W.Taylor Accession 69.580 [ANIC32-066398] (WAM).

Etymology
Late Latin inconspicuus (‘not conspicuous’); adjective in the nominative case.

References based on Global Ant Biodiversity Informatics

 * Heterick B. E., M. Castalanelli, and S. O. Shattuck. 2017. Revision of the ant genus Melophorus (Hymenoptera, Formicidae). ZooKeys 700: 1-420.