Melophorus microtriches

This ant is one of the few Melophorus that can be found in urbanized habitats, e.g., relictual woodland and rehabilitated road verges in the Perth metropolitan area. Despite its ubiquity, there are not a lot of ecological data for the species. Substrates include gravel, red soil and grey sand. Known natural habitats include mulga, riparian woodland and ‘tall woodland’, but it is also found in disturbed habitats such as paddocks, the bushier street verges and occasionally parkland native gardens. There is no information on its habits, apart from the fact it is a ground forager. (Heterick et al. 2017)

Identification
Heterick et al. (2017) - Melophorus microtriches can be placed in the Melophorus biroi species-group on the basis of characters of the clypeus, propodeum, mandible and palps. The species is also placed in the Melophorus 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 microtriches is a very matt species and has a distinctive, reticulate tibia and antennal scape. In addition, the erect setae on the metatibia are short and stout (length of longest setae < greatest width of tibia) and cannot be confused with ‘pillipes” condition setae which are long, straight and fine. In addition to the erect setae, this species possesses appressed metatibial setae that are thickly distributed and often form a distinct pubescence on the tibia. The gaster of the minor worker is also strongly pubescent. These characters combined make this species readily diagnosable.

The sequencing data are unequivocal: on a five-gene tree, M. microtriches is closely related to Melophorus hirsutipes, which it strongly resembles. Melophorus microtriches is readily recognizable by its vestiture of short, prickly setae on the body, limbs and antennal scapes, its finely sculptured antennal scape and legs and the long, overlapping, silvery appressed setae on the gaster. Typically, small minor workers are bicoloured with a dark pronotum and light-coloured mesonotum.

Distribution
Melophorus microtriches is one of the commoner members of the M. fieldi complex, and is found throughout mainland Australia.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  microtriches. Melophorus microtriches Heterick, Castalanelli & Shattuck, 2017: 283, fig. 65 (w.) AUSTRALIA.

Worker
(n = 8): CI 105–123; EI 23–31; EL 0.23–0.35; HL 0.69–1.28; HW 0.73–1.57; ML 1.06–1.72; MTL 0.65–1.00; PpH 0.12–0.17; PpL 0.43–0.72; SI 71–118; SL 0.86–1.11.

Minor. Head. Head square; posterior margin of head planar or weakly convex; frons matt or with weak sheen, shagreenate; 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 side of head capsule); in full-face view, eyes set at about midpoint of head capsule; in profile eyes set anteriad of midline of head capsule; in profile, 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 convex with anteromedial dimple; 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 matt with indistinct shagreenate sculpture throughout; anterior mesosoma in profile broadly convex; appearance of erect pronotal setae short, (i.e., longest erect setae shorter than length of eye) and unmodified; 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 about 1:1; erect propodeal setae present and abundant (greater than 12); appressed propodeal setulae long and closely aligned, creating pubescence; 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 tapered with blunt vertex; 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 variegated orange tan and brown.

Major. Head. Head square, or rectangular; posterior margin of head planar or weakly convex; cuticle of frons matt or with weak sheen, indistinctly shagreenate; 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 or weakly convex; 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 4; 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 matt or with weak sheen and microreticulate-striolate; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity between 1:1 and1:2; erect propodeal setae present and abundant (at least a dozen); appressed propodeal setae long and separated by at least own length; 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 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 variegated orange- or reddish-brown with brown gaster.

Type Material
Holotype minor worker (bottom ant) from 50 km N of Tarcoola, South Australia, 3 October 1976, P.J.M. Greenslade, (3) [ANIC32-900121]. Paratypes: 2 major workers on same pin and with same details as holotype (ANIC); media worker and major worker from 200 km NE of Alice Springs, Northern Territory, 29 May 1985 A.N. Andersen (ANIC); major worker from 76 km W of Mt Aloysius 26.06S, 127.51E, Western Australia, 16 November 1977, J.E. Feehan (ANIC); 3 minor workers from 17 km NW of Alexandria Downs 19.01S, 136.57E, Northern Territory, 13 October 1981, D. Davidson/S. Morton, 158a, lA(?), S ; major worker and 2 minor workers from 5 km SE of Oodnadatta 27.34S, 135.29E, South Australia, 4 October 1981, D. Davidson/S. Morton, 82A, A1 ; major worker and media worker from Millstream National Park 21°35'S, 117°36'E, Western Australia, 2 December 1985, P.S. Ward#, 300mm, 8069-5, ground foragers, riparian woodland ; major worker and 2 minor workers from 53 km E of Vokes Hill, Victoria Desert, South Australia, 9 October 1976, P.J.M. Greenslade, (6).

Etymology
Greek mikros (‘small’) plus pl. of trichos (‘hair’); noun in the nominative plural standing in apposition to the generic name.