Melophorus lissotriches

This species has been taken on several different types of soils (notably, red soil and brown soil plain) and vegetation zones (box-pine scrub, savanna woodland and Callitris woodland are mentioned on labels). The species has also been collected from a paddock. The ant is active at very high temperatures: five workers were collected by B. B. Lowery at 3.30pm when the temperature was 104 degrees Fahrenheit (40 degrees Celsius). He remarked that these foragers moved very fast and resembled pale Iridomyrmex. (Heterick et al. 2017)

Identification
Heterick et al. (2017) - Melophorus lissotriches 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 Melophorus mjobergi clade (within the Melophoprus biroi species-complex) but differs from the most derived species in that the major and media workers do not have the deeply recessed area around the frontal carinae and medial sector of clypeus or the impressed setae-bearing sockets visible in the heads of major and media workers of Melophorus mjobergi, Melophorus postlei and Melophorus compactus. Minor and major workers of M. lissotriches are clothed with fine, appressed silvery setae that form pubescence in the minor worker, at least, in conjunction with multiple scattered, modified erect setae (the modified setae varying from distally slightly flattened to clavate) on the head, mesosoma and gaster. This species can only be confused with its near relation, Melophorus graciliceps, but differs in having, in full-face view, the eye of the minor worker moderately convex and bulging well beyond the outline of head capsule. In profile, the mesosoma of the M. lissotriches minor worker is sinuous, the mesonotum dipping towards its junction with the propodeum and forming a weak v-shaped notch. The frontal carinae of major worker is straight or weakly convex (concave in the M. graciliceps major worker), and the cuticle of the major worker head is matt or weakly shining and minutely pitted.

Restricted sequencing (three genes) confirms its position in the M. mjobergi clade and the mtDNA sequence places it close to M. graciliceps.

Melophorus lissotriches closely resembles Melophorus graciliceps but can be recognized by the different profile and more bulbous eyes (minor worker) and the matt or weakly shining head with its straight or weakly convex frontal carinae (major worker).

Distribution
Melophorus lissotriches occurs widely in Australia and occupies the same sort of arid and semi-arid habitat as Melophorus graciliceps, but has a generally more northerly distribution and does not appear to occur in Victoria.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  lissotriches. Melophorus lissotriches Heterick, Castalanelli & Shattuck, 2017: 192, fig. 39 (w.) AUSTRALIA.

Worker
(n = 6): CI 89–105; EI 16–29; EL 0.17–0.26; HL 0.68–1.51; HW 0.60–1.58; ML 1.01–1.84; MTL 0.92–1.11; PpH 0.10–0.14; PpL 0.44–0.78; SI 62–173; SL 0.98–1.04.

Minor. Head. Head rectangular; posterior margin of head strongly convex; frons shining with indistinct microsculpture that is most pronounced on lower surfaces; frons consisting of appressed pubescence, with many short, unmodified, erect 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 around midline of head capsule; eyes elliptical or slightly reniform. In full-face view, frontal carinae concave; frontal lobes straight in front of antennal insertion. Anteromedial clypeal margin broadly and evenly convex; clypeal psammophore set at or just above anterior clypeal margin; 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 moderately shining and shagreenate 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 shining and shagreenate; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity between 1:1 and 1:2; erect propodeal setae present and sparse to moderate (1-12); appressed propodeal setulae long and closely aligned, creating pubescence; propodeal spiracle situated on or beside declivitous face of propodeum, and longer (length ≥ 0.50 × height of propodeum). Petiole. In profile, petiolar node rectangular, vertex blunt, directed posteriad; in full-face view, shape of petiolar node uniformly rounded; node shining and distinctly shagreenate-microreticulate. Gaster. Gaster weakly shining with indistinct shagreenation; pilosity of first gastral tergite consisting of thick, appressed setae that form pubescence, interspersed with numerous short, bristly, erect setae. General characters. Colour honey-brown.

Major. Head. Head quadrate (i.e., heart-shaped); posterior margin of head weakly concave; cuticle of frons matt or with weak sheen, indistinctly shagreenate; pilosity of frons a mixture of many short, erect, bristly setae interspersed with regularly spaced appressed setae. Eye small (eye length less than 0.2 × 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 weakly convex; frontal lobes curved toward 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 indistinct microsculpture that is most pronounced on lower surfaces; anterior mesosoma in profile pronotum smoothly rounded anteriad and flattened posteriad, mesonotum narrowly convex; erect pronotal setae short and often expanded distally, at times clavate; in profile, metanotal groove shallow, broadly V- or U-shaped; propodeum shining and shagreenate; propodeum always smoothly rounded; propodeal dorsum and declivity confluent; erect propodeal setae present and abundant (at least a dozen); appressed propodeal setae long and closely aligned, creating pubescence; 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 uniformly rounded, or generally rounded with median indentation; node shining and faintly shagreenate-microreticulate. Petiole. In profile, petiolar node squamiform; in full-face view, petiolar node generally rounded with median indentation or hollow; appearance of node shining and smooth with vestigial microreticulation. Gaster. Gaster weakly shining with indistinct shagreenation; pilosity of first gastral tergite consisting of short, bristly, erect setae over well-spaced, short, appressed setae. General characters. Colour of foreparts orange, gaster tawny-brown with more orange towards the sclerite margins.

Type Material
Holotype minor worker (bottom ant) from St George (‘Saint George’-sic), Queensland, 23 January 1966, B.B. Lowery, sav. Woodland, ANIC Ants Vial 20.214 [ANIC32-900148]. Paratypes: Major and minor worker on same pin and with same details as holotype (ANIC); major and minor worker from 10 km E of Mt Ive HS, Gawler Ranges, South Australia, 2 October 1980, P.J.M. Greenslade, A2 SA ; 3 minor workers from 12 km E of Emu, Victoria Desert, South Australia, 5-10 October 1976, P.J.M. Greenslade, Casuarina ; 2 minor workers from Koonamore, South Australia, 24-27 February 1973, P.J.M. Greenslade, pitfall traps, 2) [ANIC32-900131] (MCZ); minor worker from Chandlers Breakaway, Western Australia, 16 September 1988, B. Heterick, soil, native vegetation, rural environment, 452, 8MelBH33 (SAM); 2 major workers and a minor worker from Black Swan Mine 30°28'S, 121°43'E, Western Australia, 11 December 2003-5 January 2004, P. Langlands/J. Osborne; Site data C2:5 [JDM32-004807].

Etymology
Greek lissos (‘smooth’, ‘polished’) plus pl. of trichos (‘hair’); noun in the nominative plural standing in apposition to the generic name.