Melophorus anderseni Agosti

Heterick, Brian E., Castalanelli, Mark & Shattuck, Steve O., 2017, Revision of the ant genus Melophorus (Hymenoptera, Formicidae), ZooKeys 700, pp. 1-420 : 134-137

Melophorus anderseni Agosti

Melophorus anderseni Agosti 1997: 163, figs 4, 5 (w.q.)

Types.

Holotype minor worker, paratype minor workers male and queen, TERC site, Darwin, Northern Territory [ANIC] [CASC] (examined: ANIC holotype (middle ant) CASENT0172008, paratype minor worker CASENT0172007 on the same pin, one worker of Iridomyrmex sanguineus on the same pin as holotype and paratype with a label indicating association of the two species, ANIC paratype queen and two minor workers CASENT0172009, AntWeb image of paratype male [CASC] CASENT0173921.

Other material examined.

Northern Territory: Darwin (Shattuck, S.O. [ANIC32-066666]), Mudginberri (Andersen, A.N. [ANIC32-066653]).

Diagnosis.

Melophorus anderseni is a member of the M. anderseni species-group (maxillary palp segments short [not reaching neck sclerite], narrow and terminating in a subulate [awl-shaped] segment; PF 6,4; metatibial apical spur absent; in full-face view, masticatory margin of mandible strongly oblique with four teeth in known major workers [except chrysus ], and four to six teeth in minor worker). This species is distinguished from three other members of the group by having a thick, rectangular or quadrate petiolar node in the minor worker, the anterior clypeal margin broadly convex and protrusive; the clypeal psammophore located below the midline of the clypeus (major worker) or near its anterior margin (minor worker) and in having the antennal scape of minor worker devoid of erect setae. The species is confined to northern Australia.

Minor worker description.

Head. Head approximately oval with straight sides; posterior margin of head planar or weakly convex; frons matt or with weak sheen, shagreenate; frons consisting almost completely of appressed setae that may form pu bescence (tiny, erect setae, if present, usually confined to ocular triangle). 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 antennal insertion. Anteromedial clypeal margin broadly and evenly convex and protrusive; clypeal psammophore set at or just above anterior clypeal margin; palp formula 6,4. Four to five mandibular teeth in minor worker; mandibles narrow, strap-like, internal and external margins parallel or nearly so; third mandibular tooth distinctly shorter than apical tooth and teeth numbers two and four; masticatory margin of mandibles strongly 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 a weak or vestigial furrow; propodeum shining and shagreenate; 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 nearer to midpoint of propodeum than to its declivitous face, and shorter (length <than 0.50 × height of propodeum). Petiole. In profile, petiolar node cuboidal, rounded above; in full-face view, shape of petiolar node uniformly rounded; node shining and distinctly 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 reddish-brown, gaster slightly darker.

Major worker description.

Head. Head square; posterior margin of head planar or weakly convex; cuticle of frons shining and smooth except for piliferous pits; 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, midpoint of head capsule; in profile, eye set anteriad of midline of head capsule; eyes elliptical. In full-face view, frontal carinae distinctly concave, frontal lobes curved toward antennal insertion. Anterior clypeal margin broadly and evenly convex; clypeal psammophore set at or above midpoint of clypeus; palp formula 6,4. Mandibular teeth in major worker always four; mandibles narrow, strap-like, internal and external borders parallel or nearly so; third mandibular tooth distinctly shorter than apical tooth and teeth numbers two and four; masticatory margin of mandibles strongly 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, indicated mainly by an angle and metathoracic spiracles; propodeum shining and shagreenate; 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 closely aligned, creating pubescence; propodeal spiracle situated nearer to midpoint of propodeum than to its declivitous face, and shorter (length less than 0.50 × height of propodeum). Petiole. In profile, petiolar node narrowly conical, vertex sharply defined; in full-face view, shape of petiolar node generally rounded with median indentation; node shining and faintly shagreenate-microreticulate. Gaster. Gaster weakly shining with indistinct sha greenation; pilosity of first gastral tergite consisting of thick, appressed setae that form pubescence, interspersed with numerous short, bristly, erect setae. General characters. Colour dull orange, gaster brownish-orange.

Measurements.

Worker (n = 2): CI 98-114; EI 19-24; EL 0.25-0.32; HL 1.06-1.45; HW 1.04-1.65; ML 1.76-1.94; MTL 1.28-1.40; PpH 0.16-0.19; PpL 0.69-0.78; SI 73-135; SL 1.20-1.39.

Comments.

Only a few collections of this social parasite of Iridomyrmex sanguineus have been taken, and the description of the worker by Agosti (1997) is in informal, telegraphic style, and is characterized more formally here for the first time. The behavior of M. anderseni in raiding nests of I. sanguineus has been well documented by the same author ( Agosti 1997). TERC material has been taken in Kakadu, Kidman Springs, the Ranger Uranium Mine lease (NT), Mt Isa and Tin Camp Creek (QLD). All ANIC collections have been taken in the NT, but the ant may also occur in the Kimberley region of WA (at least) where populations of its host also occur. The apparent rarity of the species may be due to under collection because of its very specialized habits. Melophorus anderseni has several apomorphic characters shared only by the following species (notably very short palps and an absent metatibial apical spur), but its position within the genus as a whole is uncertain in the absence of genetic sequencing. However, the morphology suggests it is not close to the M. aeneovirens group. A possible close relationship with the M. fieldi group and, in particular, the M. fieldi complex is indicated by the presence of an anteromedian dorsal lip or protuberance in the queen (though not the workers).