Melophorus lanuginosus 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 : 237-240

Melophorus lanuginosus Heterick, Castalanelli & Shattuck sp. n.

Types.

Holotype minor worker (bottom ant) from Fowler’s Gap, New South Wales, 19 November 1979, (8) [ANIC32-900145] (ANIC). Paratypes: 2 major workers on same pin and with same details as holotype (ANIC); major and media worker from Kunoth Paddock, near Alice Springs, Northern Territory, 3-6 March 1975, P.J. M. Greenslade, Traps Hills, 5 (BMNH); major worker and media worker from Kunoth Paddock, near Alice Springs, Northern Territory, 26 October 1974, P.J. M. Greenslade, Traps Hills, 11 (MCZ); major worker and 2 minor workers from 17 km SE of Oodnadatta, South Australia, 24 September 1972, J.E. Feehan (SAM); major worker, media worker and 2 minor workers from Coorow 29°56'S, 116°03'E, Western Australia, 2 October 1999, B.E. Heterick, white sand [JDM32-001806] (WAM); major worker, 2 media workers and minor worker from Ethel Creek, Western Australia, 1993-4, P.A. Varris, nest 12, Melophorus sp. A [JDM32-001794] (WAM).

Other material examined.

New South Wales: Fowlers Gap (Greenslade, P.J. M. ). Northern Territory: Kunoth Paddock, near Alice Springs (Greenslade, P.J. M. ), Kunoth Paddock, near Alice Springs (Greenslade, P.J. M. ). South Australia: Burnt Camp Dam, Calperum (Medlin, G. C.). Western Australia: 0.9 km along Tanami Rd (Heterick, B.E. [M206/M207/M208]), 18.5 km E Southern Cross (Heterick, B.E. [M132/M133/M134]), Dunham River (rest area) (Heterick, B.E. [M214/M215]), Marillana Ck. (Dunlop, N. [JDM32-001823]), Miling (Heterick, B.E. [M302/M303]), Panawonica [Pannawonica] (Brown, K. [JDM32-001827]), Pilbara Locality (collector unknown [JDM32-001812]).

Diagnosis.

Melophorus lanuginosus can be placed in the M. biroi species-group on the basis of characters of the clypeus, propodeum, mandible and palps. The species is also placed in the M. 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. In general, Melophorus lanuginosus is rendered distinctive by a combination of its long white setae, which form a thatch on the gaster and on the pronotum, the long erect setae on the mesosoma (longer setae> diameter of eye); cuticle with strong shagreenate sculpture, matt or with weak sheen and a relatively thick petiolar node in the minor worker (to about 0.6 × as wide as high). Neither is the petiolar node a true scale in the major worker. In most specimens the anteromedial dimple is prominent and protrudes as a V-shaped lip. These features combined are found only in this species. In addition to these features, the " pillipes " form has whorls of fine, straight erect setae on the legs and antennal scape. A second variant found at a couple of sites in NW Australia has aberrant major and media workers. These possess a short, protrusive flange on the midline of the capsule between the frontal carinae, and frons adjacent to the frontal carinae is recessed as in the M. mjobergi clade major workers. Additionally in these subcastes, the torulus is bizarrely produced as a sleeve to the base of the antennal scape and its pedicel. Apart from these particular features, these two variant conform to the diagnosis of the typical M. lanuginosus .

Minor worker description.

Head. Head square; posterior margin of head planar or weakly convex; frons shining with superficial shagreenation or microreticulation only, or matt or with weak sheen, microreticulate or microreticulate-shagreenate; pilosity of frons a mixture of short, erect and semi-erect setae interspersed with shorter decumbent setae and well-spaced, short, appressed 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, or set at about midpoint of head capsule; in profile, eye set anteriad of head capsule, or set around 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 long (i.e., longest erect setae longer than length of eye) and unmodified; in profile, metanotal groove shallow, indicated mainly by an angle; propodeum matt or with a weak sheen and indistinctly shagreenate; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity about 4:3, or about 1:1; erect propodeal setae present and abundant (greater than 12); appressed propodeal setulae long and closely aligned, creating pubescence, or long, each reaching setae behind and in front, but not forming 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, or subcuboidal, vertex bluntly rounded; in full-face view, shape of petiolar node uniformly rounded, or tapered with blunt vertex; node shining and smooth with vestigial sculpture, or matt and microreticulate. Gaster. Gaster weakly shining with indistinct shagreenation, or shining, shagreenate ('LP record’ appearance); pilosity of first gastral tergite consisting of a mixture of curved, erect and semi-erect setae and decumbent and appressed setae that form a variable pubescence. General characters. Colour various shades of orange or brown, usually concolorous but gaster may be darker.

Major worker description.

Head. Head horizontally rectangular, broader than wide; posterior margin of head planar or weakly concave; cuticle of frons matt or with weak sheen, indistinctly shagreenate; pilosity of frons a mixture of well-spaced, distinctly longer erect and semi-erect setae interspersed with shorter decumbent setae. 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 four; 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 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 of foreparts various shades of light tan with brown gaster.

Measurements.

Worker (n = 6): CI 103-116; EI 21-31; EL 0.20-0.35; HL 0.61-1.45; HW 0.62-1.69; ML 0.92-1.22; MTL 0.67-1.22; PpH 0.10-0.19; PpL 0.37-0.65; SI 72-130; SL 0.81-1.22.

Comments.

In appearance this very hairy member of the M. fieldi complex most closely resembles M. hirsutipes , but the presence of long, silvery, overlapping appressed setae on the pronotum and first gastral segment and the narrower, more porrect petiolar node help to distinguish this ant from the former. The anteromedian clypeal prominence is strongly developed in many populations of this species. Despite its morphological similarity to M. hirsutipes , M. lanuginosus appears to be most closely related to M. longipes , and forms a sister relationship to that species on a five-gene tree - but see ‘Comments’ for the latter.

A small number of samples of workers of all subcastes from Packsaddle in the Pilbara, WA, reveal a strange development of the torulus. The torulus is merely produced as a short stalk in minor and media workers but in the major worker the lobes of the frontal carinae have become raised and invaginated to form ragged, projecting narrow sleeves to which the torulus is fused. The torulus further protrudes to surround the antennal condyle. This is analogous to the situation in M. hirsutus . The area around the frontal carinae is also recessed in the major worker. The end result is an ant of hybrid appearance that is not dissimilar in regard to its cephalic morphology to M. mjobergi or M. postlei . In addition, major and media workers, but not the minor workers, have a protruding flange that juts from the midline of the head within the frontal triangle (this area generally appears as a smooth, shining, unsculptured band in most Melophorus ). The major also has a slightly more hunched appearance than the major workers of normal M. lanuginosus . In all other respects of their morphology, however, these workers resemble normal workers of M. lanuginosus . The reasons for this strange appearance are unknown and can only be guessed at. Hybridization with a species in the M. mjobergi complex seems unlikely because of their lack of relatedness to M. lanuginosus .

The species is well-distributed throughout drier inland habitats in NSW, NT, SA and WA, but does not appear to occur in QLD or Vic. In Southern Cross, WA, specimens have been taken in heathland on top of yellow sand, and from a lawn in the little WA wheatbelt town of Miling. Two workers were collected from a dune in Burnt Camp Dam, SA (SAM). No other meaningful data are available. In the field, this species appears similar to M. turneri , but is less shiny.

Etymology.

Latin lanuginosus ( ‘woolly’ or ‘downy’); adjective in the nominative singular.