Melophorus solitudinis

The ant is known from just three workers from two sites in inland WA. Despite the paucity of material, the ant may not be rare: because of its remote habitat it is unlikely to be seen by the majority of collectors. Nothing is known of its habits. (Heterick et al. 2017)

Identification
Heterick et al. (2017) - Melophorus solitudinis 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. In Melophorus solitudinis the body of both the major and the minor worker are clothed with modified, erect setae (distally thickened, clavate or spatulate) to various degrees in addition to unmodified setae. In full-face view, the heads of the major and minor worker are matt with microreticulate sculpture. These features separate this taxon from most others. The major worker of this species is more densely sculptured than are Melophorus bruneus and Melophorus fieldi, the M. solitudinis minor worker is much larger than the minor workers of those two species, and its weakly divergent frontal carinae distinguish this ant from Melophorus setosus.

Melophorus solitudinis is a fairly squat, dull species that is characterized by a combination of erect setae on the tibiae, modified setae on the head and mesosoma and densely shagreenate sculpture of the cuticle. The appearance of the setae is not unlike that found in M. setosus, but the two species are unlikely to be closely related.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  solitudinis. Melophorus solitudinis Heterick, Castalanelli & Shattuck, 2017: 305, fig. 71 (w.) AUSTRALIA.

Worker
(n = 2): CI 109–117; EI 19–24; EL 0.26–0.34; HL 0.99–1.37; HW 1.08–1.59; ML 1.34–1.67; MTL 0.89–1.09; PpH 0.17–0.24; PpL 0.54–0.71; SI 78–99; SL 1.07–1.24.

Minor. Head. Head square; posterior margin of head planar or weakly concave; frons 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 or weakly convex; frontal lobes straight in front of antennal insertion. Anteromedial clypeal margin broadly and evenly convex; clypeal psammophore set below midpoint of clypeus; palp formula 6,4. Five mandibular teeth in minor worker; 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; anterior mesosoma in profile broadly convex; appearance of erect pronotal setae short and often expanded distally, at times clavate; in profile, metanotal groove shallow, broadly V- or U-shaped; propodeum matt or with a weak sheen and microreticulate; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity about1:1; erect propodeal setae present and abundant (greater than 12); appressed propodeal setulae long and separated by at least own length; 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 tapered with blunt vertex; node matt and microreticulate. Gaster. Gaster weakly shining and microreticulate; pilosity of first gastral tergite consisting of well-spaced, short, thick, erect setae over long, closely aligned, whitish, appressed setae. General characters. Colour of foreparts and legs orange-tan, gaster brown.

Major. Head. Head square; posterior margin of head planar or weakly concave; cuticle of frons matt or with weak sheen, microreticulate; frons consisting mainly of appressed and stout erect setae, the latter bristly in appearance and distinctly modified (flattened) distally. 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 and evenly convex; clypeal psammophore set at or above midpoint of clypeus; palp formula 6,4. Five mandibular teeth in major worker; 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 matt or with weak sheen and microreticulate throughout; anterior mesosoma in profile broadly convex; erect pronotal setae short and often expanded distally, at times clavate; in profile, metanotal groove shallow, broadly V- or U-shaped; propodeum matt or with weak sheen and microreticulatestriolate; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity about 1:1; 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 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 tapered with blunt vertex; node shining and faintly shagreenate-microreticulate. Gaster. Gaster shining with superficial microreticulation; pilosity of first gastral tergite consisting of longish, closely aligned, appressed setae interspersed with short, bristly, erect setae (some distally flattened). General characters. Colour of foreparts and legs orange-tan, gaster brown.

Type Material
Holotype minor worker from Tropicana Minesite 29°20'27"S, 124°29'08"E, Western Australia, January 2009, J. Summerhayes, pitfall; trap: mallee MA2:1 [JDM32-004513]. Paratypes: major and minor worker from 16 miles ENE of Cosmo Newbery [sic] Mission, Western Australia, 14 October 1960, McInnes & Dowse [ANIC32-066647].

Etymology
Latin solitudinis (‘loneliness’): a reference to the ant’s remote habitat; adjective in the nominative case.