Melophorus perthensis

This is a very common species and one of the few Melophorus for which there is detailed ecological information.

Identification
Heterick et al. (2017) - Melophorus perthensis 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 perthensis is a relatively large (HW 0.72–1.92 mm), smooth and shiny species. The appressed setae on the gaster are very small and well-separated. This ant is most likely to be confused with some populations of Melophorus turneri. However, when viewed in profile, the smoothly rounded pronotum and the mesonotum that is elongate and broadly convex and arches above the level of the pronotum in all workers make this ant distinctive in most cases. In a few eastern states populations of M. turneri the pronotum and mesonotum are strongly convex, but these workers do not possess the very truncate propodeum seen in M. perthensis that usually arises above the metanotal groove.

Melophorus perthensis is characterized by the rounded mesonotum, giving this sclerite an arcuate appearance in profile. In some populations, particularly on the east coast, this trait is not so accentuated, and other characters are required to discriminate between the species and its relatives, particularly Melophorus turneri. The truncated propodeum is commonly helpful for identifying minor workers, and M. perthensis is generally larger than M. turneri (ML 1.06–2.02 mm compared with 0.90–1.57 mm). This species has been recorded from all mainland Australian states except Victoria, but probably also occurs there. However, its occurrence in Tasmania is problematic. Genetically, the ant is distinct from M. turneri. However, on individual gene trees, members of this taxon cluster close to some M. turneri populations.

Distribution
Heterick (2009) - Broad distribution in WA, though they have most often been collected in the southwest of the State.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Biology
Wheeler (1934) - Common in the sandy portions of King's Park, Perth, which may be regarded as the type-locality. Like most other species of Melophorus it makes flat, excentric crater nests.

Heterick (2009) - Familiar to many Perth city dwellers, even those without an entomological interest. This species is the Melophorus most commonly seen in and around the city in summer, when it is active on sandy verges, urban dune systemsand backyards. The amount of sand displaced by this ant is considerable. Workers can often be seen taking grass seeds, other plant material and occasionally small carrion back to their nests. Under a microscope, workers of this species can be identified by their bulbous mesonotum.

Heterick et al. (2017) - Melophorus chauliodon and Melophorus perthensis are by far the two most common Melophorus in the Perth metropolitan area, frequently occur together and bear a superficial resemblance to one another.

Majer et al. (2011) found M. perthensis was a key dispersal agent of seeds in a variety of woodland sites in the Darling Plateau and the Swan Coastal Plain between Perth in the north and Manjimup in the south (Two other non-Melophorus ants were also studied). Major findings connected with M. perthensis were as follows:

• this species was seasonally active between October and April, with peaks of activity in December and January. No activity was recorded between May and September,

• peak diurnal activity was in the early afternoon,

• fire caused a decline in activity in three out of four site studied, with 1.7 times as many individuals active before burns than after burns,

• this species prefers low ground cover and low understorey shade for its nest sites,

• the nests themselves comprise a vertical channel with a series of side galleries at regular intervals,

• mean number of workers per nest was 230.4,

• food items comprised seeds (29.1% of forage), miscellaneous plant fragments (25.3%) and invertebrates (54.6%),

• regression models relating ant foraging activity to myrmechore flowering revealed a four month lag time, and

• seedling emergence was much higher around nests of this species (and other ant nests) than elsewhere.

The researchers also found nests of this species in the sandplain were deeper than in lateritic soils, and colony sizes were much lower than for Melophorus bagoti. Label data reveals these ants can be found in mallee scrub and in red soil in other parts of Australia. This species is the commonest Melophorus found in the Perth metropolitan area, along with M. chauliodon. In the summer season, active nests can be seen in sandy soils in yards, gardens, beside footpaths, and, indeed, in any area where there is sufficient soil for ants to nest. Probably because of its thermophilic behavior, this is one native ant species that is not fazed by the presence of aggressive invasive exotics such as the Big-headed ant Pheidole megacephala and the Argentine ant Linepithema humile.

Nomenclature

 *  perthensis. Melophorus turneri subsp. perthensis Wheeler, W.M. 1934d: 152 (s.w.) AUSTRALIA.
 * Subspecies of turneri: Taylor & Brown, 1985: 125; Bolton, 1995b: 250; Heterick, 2009: 98.
 * Status as species: Heterick, et al. 2017: 293 (redescription).

Worker
minor Length 3-3.5 mm.

Very similar to the worker major but the smaller head is proportionally narrower, being about one-fourth broader than long. Antennal scapes extending nearly half their length beyond its posterior border. Promesonotum less, base of epinatum more convex, the latter longer in proportion to the declivity. Petiolar scale decidedly thicker, lower and blunter, scarcely produced at the summit, which is impressed but not emarginate.

Sculpture and pilosity as in the worker major; head, thorax and petiole, darker and more brown, as are also the appendages.

major Length 4.5-5 mm.

Very similar to the subspecies Melophorus turneri candidus from Victoria but somewhat larger, with mandibles more strongly bent at the base, antennal scapes extending somewhat more than twice their greatest diameter beyond the posterior border of the head and the clypeal border more produced in the middle and not emarginate. Petiolar scale prolonged and narrowed upward, with distinctly emarginate superior border. Epinotal base and declivity forming a distinct obtuse angle in profile, the former convex: and little more than half as long as the straight, sloping declivity. Pilosity much less developed than in candidus, absent on thorax and petiole and very short and sparse on the legs, the tibiae with a row of four or five bristles on their flexor surface-so Head, thorax, petiole, coxae and antennae ,brownish red or reddish brown, legs brighter yellow or less reddish than in candidus. Gaster with metallic blue-green reflections which are quite as vivid as in the typical turneri, posterior edges of segments yellowish.

Heterick et al. (2017) - (n = 8): CI 97–119; EI 17–32; EL 0.23–0.33; HL 0.74–1.61; HW 0.72–1.92; ML 1.06–2.02; MTL 0.69–1.36; PpH 0.11–0.19; PpL 0.44–0.74; SI 70–123; SL 0.89–1.35.

Minor. Head. Head square; posterior margin of head planar or weakly convex; frons shining with superficial shagreenation or microreticulation only; 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 distinctly concave; 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 with weak to moderate sheen and superficial microreticulation (more pronounced on mesopleuron); 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 deep, V-shaped; propodeum shining and finely striolate and microreticulate; propodeum always smoothly rounded; propodeal dorsum and declivity confluent; erect propodeal setae variable in number, may be absent; appressed propodeal setulae short, separated by more than own length and inconspicuous; propodeal spiracle situated on or beside declivitous face of propodeum, and shorter (length < 0.50 × height of propodeum). Petiole. In profile, petiolar node squamiform, or subcuboidal, vertex bluntly rounded; in full-face view, shape of petiolar node uniformly rounded; node shining and smooth throughout. Gaster. Gaster shining, shagreenate (‘LP record’ appearance); pilosity of first gastral tergite consisting of well-spaced, erect and semi-erect setae interspersed with regularly placed appressed setae. General characters. Colour of foreparts brown, gaster usually dark 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; 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 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 concave; 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 shining with indistinct microsculpture that is most pronounced on lower surfaces; anterior mesosoma in profile broadly convex; erect pronotal setae long (i.e., longer than length of eye) and unmodified, or 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 smoothly rounded or with indistinct angle; propodeal dorsum and declivity confluent; erect propodeal setae present and sparse to moderate (1-12); 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 generally rounded with median indentation, node shining and faintly shagreenate-microreticulate. Gaster. Gaster weakly shining with indistinct shagreenation; pilosity of first gastral tergite consisting of well-spaced, erect and semi-erect setae interspersed with regularly spaced appressed setae. General characters. Colour reddish-brown, gaster darker.

Type Material
Heterick et al. (2017) - Syntype major and minor workers: Rottnest Island and Kings Park, Western Australia (examined: images taken by S.O.Shattuck of MCZ specimens “cotype’ 23042, MCZ-ENT 00303602 [Kings Park] and “cotype’ 23042 [Rottnest Is.]. (Note. Series MCZ-ENT 00303602 includes a major worker of M. chauliodon.)

As with Melophorus sulla, the type material reveals confusion, with more than one species included in the syntype series. A media or small major worker collected in Kings Park, Western Australia on 20 October 1931 by the Harvard Australian Expedition led by William Morton Wheeler and held at MCZ (‘co-type 23042’) is actually Melophorus chauliodon