Melophorus praesens Heterick, Castalanelli & Shattuck

Heterick, Brian E., Castalanelli, Mark & Shattuck, Steve O., 2017, Revision of the ant genus Melophorus (Hymenoptera, Formicidae), ZooKeys 700, pp. 1-420 : 105-109

Melophorus praesens Heterick, Castalanelli & Shattuck sp. n.

Types.

Holotype minor worker (top ant) from 85 km W of Mabel Creek, South Australia, 8-10 October 1980, P.J. M. Greenslade pt B, 24) [ANIC32-900179] (ANIC); Paratypes: 2 minor workers on same pin and with same details as holotype (ANIC); minor worker from 109.5 km SE Newman, 23°52'59"S, 120°38'31"E, Western Australia, June 1986, S. van Leeuwen & R.N. Bromilow, [JDM32-001483], Curtin University JDM Collection, donated 12 Jan. 2015 (BMNH); minor worker from 85 km W Mabel Creek, South Australia, 8-10 October 1980, P.J. M. Greenslade, Pt A, 23), Melophorus sp. 6 loan ANIC 1991 (MCZ); 3 minor workers from Sandringham, [SW] Queensland, February 1980, P.J. M. Greenslade leg. Morton, (10) (QM); 2 minor workers from 30 km E Poeppel Corner, Simpson Desert, South Australia, 25 August 1977, P.J. M. Greenslade (ANIC32-900083) (SAM); minor and 2 major workers from 24 miles ESE of Broome, 17 April 1963, McInnes & Dowse, 28706, Central & NW Aust. 1963, Series A223 (WAM).

Other material examined.

Queensland: 40 km E Cameron Corner (Greenslade, P.J. M. ), Sandringham (Morton, S.). South Australia:, 3 minor workers (one broken in two) from Brookfield, South Australia, 29 October 1991, (Shattuck, s. [#2506.6]); 10 km E Mt Ive HS, Gawler Ranges, South Australia, (Greenslade, P.J. M. ), Mt Serle Stn, 2.3 km SSE Moosha Bore (Flinders Ra surv REH0501). Victoria: 6.3 km N Hattah (Yen, A.L. [M109]). Western Australia: 8 km N Bullfinch (Heterick, B.E. [M130/M131]), Theda/Doongan, North Kimberley (Cross, A.) [not on map], Derby (Dodd, W.D.), Kojonup (Majer, J.D. [JDM32-001474]), Pardoo Stn turnoff (Heterick, B.E. [M266]), Tutanning, (Perth, A. [JDM32-001480] [major worker - imaged, this work]).

Diagnosis.

Melophorus praesens is a member of the M. 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 M. 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), and the M. aeneovirens species-complex (in full-face view, psammophore ranged along or just above anterior margin of clypeus and following the curve of the margin; anterior margin of clypeus broadly medially produced, and often with central notch that may be deeply impressed, but is never acuminate at its midpoint; metatibia with maximum of two rows of preapical spines). In M. praesens the tibiae possess stout, socketed, appressed to subdecumbent setae only, with fine, appressed pubescence lacking. In profile, the mesosoma of the minor worker tends to linear in orientation, its dorsal outline straight or describing a weak arc (the mesosternal outline and the dorsum of the mesonotum being weakly convergent to subparallel anteriorly). Melophorus praesens is almost identical to M. clypeatus but can be distinguished from that species by the less protrusive clypeus in both major and minor workers. Minor workers of Melophorus praesens can be distinguished from those of the similar M. castaneus by the asymmetrical appearance of the vertex and by the overlapping appressed setae on the gaster, and from minor workers of M. rufoniger by their smaller size ( M. rufoniger HW of major worker>3 mm, HW of minor worker> 1 mm; M. praesens HW of major worker ≤ 2.3 mm, HW of minor worker <1 mm) and the less protrusive medial sector of the clypeus.

Minor worker description.

Head. Head approximately oval with straight sides; 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; frontal lobes straight in front of anten nal insertion. Anteromedial clypeal margin narrowly convex and protruding, clypeal midpoint distinctly notched; clypeal psammophore set at or just above anterior clypeal margin; palp formula 6,4. Five mandibular teeth in minor worker; mandibles trian gular, 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; erect pronotal setae absent; in profile, metanotal groove deep, ‘V’ -shaped, or shallow, broadly V or U-shaped; propodeum shining and shagreenate; propodeum smoothly rounded or with indistinct angle; propodeal dorsum and declivity confluent; erect propodeal setae always absent; appressed propodeal setulae long, each reaching setae behind and in front, but not forming pubescence; propodeal spiracle situated on or beside declivitous face of propodeum, and shorter (length <0.50 × height of propodeum). Petiole. In profile, petiolar node subcuboidal, vertex bluntly rounded; in full-face view, shape of petiolar node uniformly rounded; node shining and smooth with vestigial sculpture. Gaster. Gaster shining, shagreenate ('LP record’ appearance); pilosity of first gastral tergite consisting of well-spaced, long, whitish, appressed setae only, erect setae always absent. General characters. Two main colour forms: concolorous chocolate, and orange-tan with chocolate gaster.

Major worker description.

Head. Head quadrate (i.e., heart-shaped); posterior margin of head planar or weakly concave; cuticle of frons shining with superficial shagreenation or microreticulation only, or matt or with weak sheen, indistinctly 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 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 straight, divergent posteriad; frontal lobes straight in front of antennal insertion. Anterior clypeal margin narrowly convex and protruding anteromedially, clypeal margin entire or weakly indented; clypeal psammophore 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 convex anteriad, mesonotum overlapping pronotum, planar or slightly sinuate posteriad; erect pronotal setae short, (i.e., shorter than length of eye) and unmodified; in profile, metanotal groove shallow, broadly V- or U-shaped; propodeum shining and microreticulate; propodeum smoothly rounded or with indistinct angle; propodeal dorsum and declivity confluent; erect propodeal setae present and sparse to moderate (1-12); appressed propodeal setae long and closely aligned, creating pubescence, or long, each reaching setae behind and in front, but not forming pubescence; 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; node shining and smooth with vestigial microreticu lation anteriad. Gaster. Gaster shining, shagreenate ('LP record’ appearance); 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 tan or reddish chocolate, gaster brown to chocolate.

Measurements.

Worker (n = 6): CI 86-108; EI 17-28; EL 0.24-0.38; HL 0.99-2.13; HW 0.85-2.31; ML 1.63-2.65; MTL 0.97-1.60; PpH 0.18-0.25; PpL 0.78-1.31; SI 76-157; SL 1.34-1.76.

Comments.

Melophorus praesens has a very broad distribution throughout Australia: records have come from all mainland states except NSW, but it probably occurs there as well. This species sensu lato can be distinguished from others in the M. aeneovirens complex by a combination of its asymmetrical head capsule, the shape of the propodeum and the conformation of the clypeus (not as protrusive as that of the very similar M. rufoniger , and resembling more that found in M. aeneovirens in most specimens). The tibiae completely lack fine, appressed pubescence in the northern topics and desert form, but there may be a few tiny setae, especially at the base of the tibia, that can be seen in some lights, in the southern form. A five-gene tree places this species as sister to M. rufoniger , which it very closely resembles. This ant has mainly been collected in arid and semi-arid areas. In more mesic localities it is replaced by M. aeneovirens . Labels reveal little in the way of additional data, but the species has a generalized morphology typical of the group and probably has habits to match. Collections have been made from a variety of habitats. One specimen hand collected near Pardoo, WA, was active in thundery conditions on a recently burnt plain, while another specimen was hand collected in Bullfinch, WA on red loam soil. Yet another sample was collected at Mt Serle Stn, SA, from a creek line in low rocky hills.

Note: what is here called ' praesens ' reveals perhaps two forms that can only be distinguished by very subtle differences in the length and appearance of the appressed setae on the tibiae and gaster. Paratypes have been chosen that unequivocally match the holotype (northern/desert form), which has sparse, stout appressed setae on the tibiae and short appressed setae on the gaster that are mostly separated by more than their own length and do not form pubescence. All paratypes have orange-brown foreparts and brown gasters. There is the possibility that the hairier southern form (which has shining, elongate setae on the gaster that may form a weak pubescence, and a few minute appressed setae on the tibiae among rather elongate, fine appressed setae) is genetically distinct, and may constitute a western population of M. curtus , which it closely resembles in general morphology. In some series with dark brown minor workers the metanotal groove is deeply impressed and the propodeum has a marked anterior peak. Specimens have mainly been taken from south-west WA in drier areas and the south-east corner of SA. Further adding to the complication, the specimens from Brookfield (SA) and Junana Rock (WA), are particularly hirsute and have fine pubescence on the mesosoma in addition to the long, fine appressed setae on the gaster. Insufficient specimens have been sequenced (none of indubitable M. curtus ) to do more than flag these apparent subtle differences here for future investigation.

Etymology.

Latin praesens ('at hand’); participle in the nominative singular.