Melophorus gracilipes

Melophorus gracilipes is an ant of the arid and semi-arid areas, and is absent from the wetter parts of the southern coastline. As with other common species in the M. aeneovirens species-group, M. gracilipes has been found in a wide range of phytogeographic zones including hummock grasslands, mulga woodlands, acacia woodlands with spinifex, and sclerophyll woodlands. Red clay soil seems to be a favoured substrate for its nests. This species is a scavenger: a couple of workers hand collected near Pamellia Hill, WA, were carrying a dead grasshopper. (Heterick et al. 2017)

Identification
Heterick et al. (2017) - Melophorus gracilipes is a member of the Melophorus aeneovirens species-group (in full-face view, the anterior clypeal margin convex, apron-like and covering whole or part of the retracted mandible, except in Melophorus nemophilus, the medial clypeal sector often produced so that it is protrusive when seen in profile; the psammophore frequently with coarse and well-separated ammochaetae, these always placed on or just above anterior margin; in profile, the propodeum elongate and oblique or broadly rounded). The ant is also placed as a member of the Melophorus bagoti complex because of the acuminate appearance of the midpoint of the anterior clypeal margin. In full-face view, the psammophore occurs as a row of long, thick setae set slightly above the anterior clypeal margin. Unlike its sister species, M. bagoti, M. gracilipes has just two rows of preapical tibial spines on the metatibia.

Superficially, this large species resembles large members of the M. aeneovirens complex, but the appearance of the clypeus is sufficient to place it in the M. bagoti complex, and genetic sequencing data confirms this placement. The ant can easily be distinguished from M. bagoti by its more gracile appearance and the presence of two rows of preapical spines on the metatibia (five rows in M. bagoti). As with M. bagoti, the colour of the gaster in this taxon can vary from yellowish orange and concolorous with the rest of the ant to an iridescent black, with various shades in between. (In the case of M. bagoti, nest series of the most strikingly bicoloured ants seem to be of the one colouration, but workers of other nests can nonetheless show variation in colour between light orange gaster and blackish-orange gaster morphs).

Distribution
Mainland records all have come from WA, although it likely also occurs in western parts of the NT and SA.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  gracilipes. Melophorus gracilipes Heterick, Castalanelli & Shattuck, 2017: 138, fig. 24 (w.) AUSTRALIA.

Worker
(n = 8): CI 101–120; EI 15–21; EL 0.29–0.44; HL 1.36–2.54; HW 1.38–3.04; ML 2.44–4.11; MTL 2.47–2.84; PpH 0.21–0.47; PpL 1.04–1.70; SI 89–153; SL 2.11–2.69.

Minor. Head. Head approximately oval, sides of head divergent towards mandibular articulations; posterior margin of head extended posteriad as a convex, sloping surface with a slight medioccipital protuberance; 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. In full-face view, frontal carinae straight or weakly convex, or straight, convergent posteriad; frontal lobes curved toward antennal insertion. Anteromedial clypeal margin convex, weakly acuminate anteromedially; clypeal psammophore set below midpoint of clypeus, or set at or just above anterior clypeal margin; palp formula 6,4. Five to six 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 convex anteriad, mesonotum often slightly overlapping pronotum, mesosoma planar or slightly sinuate posteriad; erect pronotal setae absent; in profile, metanotal groove shallow, broadly V or U-shaped; propodeum shining and uniformly striolate; propodeum always smoothly rounded; 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). Petiole. In profile, petiolar node a broadly right angled triangle with steeply declivitous posterior face; in full-face view, shape of petiolar node uniformly rounded, or square with rounded angles; node shining and faintly striolate and microreticulate. Gaster. Gaster shining, shagreenate (‘LP record’ appearance); pilosity of first gastral tergite consisting of well-spaced short, inconspicuous, appressed setae only, erect setae always absent. General characters. Colour variable, pale yellow to brown.

Major. Head. Head square; posterior margin of head planar or weakly convex; cuticle of frons 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 above midpoint of head capsule; in profile, eye set anteriad of midline of head capsule; roughly ovoid, eye narrowed posteriad. In full-face view, frontal carinae straight or weakly convex, or straight, convergent posteriad; frontal lobes straight in front of antennal insertion, or curved inward in front of antennal insertion. Anterior clypeal margin convex, acuminate anteromedially, margin entire; clypeal psammophore set below midpoint of clypeus, or set at or just above anterior clypeal margin; 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 with weak to moderate sheen, shagreenate on pronotum and dorsum of mesonotum, otherwise microreticulate; anterior mesosoma in profile broadly convex, or convex anteriad, mesonotum overlapping pronotum, planar or slightly sinuate posteriad; erect pronotal setae absent; 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 absent; appressed propodeal setae 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 less than 0.50 × height of propodeum). Petiole. In profile, petiolar node narrowly conical, vertex sharply defined, or a broadly right angled triangle; in full-face view, shape of petiolar node generally rounded with median indentation; node shining and faintly striolate and microreticulate. Gaster. Gaster shining with superficial microreticulation; pilosity of first gastral tergite consisting of well-spaced short, inconspicuous, appressed setae only, erect setae always absent. General characters. Colour concolorous light orange or russet with brown gaster.

Type Material
Holotype minor worker (bottom ant-slightly damaged) from Yamarna Homestead 28°10'S, 123°40'E, Western Australia, 16 December 1996-30 January 1997, S. Richardson, Acacia woodland with spinifex, sandy loam [ANIC32- 032240]. Paratypes: major worker and media worker on same pin and with same details as holotype (ANIC); 2 media workers from 55 miles E of Wiluna, Western Australia, 10 October 1969, McInnes & Dowse (ANIC); major worker and 2 minor workers from Murchison River, Western Australia, ‘Melophorus bagoti Lubbock, Det. J.J. McAreavey, 7 January 1960 [sic] [these specimens can easily be distinguished from M. bagoti by the the two rows of spines on the metatibia-BEH] ; 2 media workers from 10 km SE Karonie, Western Australia, 9 November 1969, Key’s field notes. Trip 163, Stop 19405.6, ground strays, evening, sclerophyll wood., R.W. Taylor ; Major worker and minor worker from 30 km S of ‘The Overlander’, Western Australia, 20 March 1987, B. Heterick, soil, native vegetation, rural environment, 183, 8MelBH1 ; 2 minor workers from Rabbit Proof Fence Road 30°26'57"S, 118°31'13"E, Western Australia, 21 November 2009, Heterick, B.E., Laterite sandplain, proteaceous heathland with small trees, by hand, early pm [JDM32-004618] (WAM).

Etymology
Latin gracilis (‘slender’) plus pes (‘foot’); adjective in the nominative singular.