Melophorus postlei 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 : 188-190

Melophorus postlei Heterick, Castalanelli & Shattuck sp. n.

Types.

Holotype minor worker from Kapalga, Northern Territory, 16 January 1983, P.J. M. Greenslade, Sai, Sa [ANIC32-900181] (ANIC). Paratypes: 3 major workers from Rimbija Is., Wessell Islands, 11.01S, 136.45 E, Northern Territory, 3-14 February 1977; T. A. Weir [ANIC32-900087] (ANIC); 2 minor workers from Kapalga (pencil), Alligator Rivers area 7-9 September 1983, P.J. M. Greenslade, 8i traps (BMNH); 2 minor workers from Manbulloo, SW Katherine, Northern Territory, 7-11 April 1978, P.J. M. Greenslade, 25 (MCZ).

Other material examined.

Northern Territory: 30 km SW Katherine (Greenslade, P.J. M. ), Avon Downs (Colles, D.H.), Kapalga (Greenslade, P.J. M. [ANIC32-900181]), Kapalga (Greenslade, P.J. M. ), Manbulloo Research Station (Gross, G.), Manbulloo, SW Katherine (Greenslade, P.J. M. ), Manbulloo, SW Katherine (Greenslade, P.J. M. [ANIC32-900086]), nr Limbunya turnoff (Heterick, B.E. [M221]), Western Australia: Dunham River (rest area) (Heterick, B.E. [M216]), 100 km N Meekatharra (Heath, M & Turpin, J. [JDM 32-004896]).

Diagnosis.

Melophorus postlei 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. mjobergi clade because of characters best seen in the major worker. These include (seen in full-face view) the deeply recessed area around the frontal carinae and medial sector of clypeus visible in the major and media workers, the psammophore generally placed on or just above anterior margin of clypeus, and the minor workers hairy with bristly, short erect setae. In Melophorus postlei the head of all workers is microreticulate and moderately shining to matt and the setae-bearing sockets on the head of the major worker are impressed so as to appear as small, oval depressions. In full-face view, the antennal carina of the major worker is limited to a flange around the antennal insertion, a weak ridge representing the posterior extension of carina is strongly concave posteriad. This will differentiate this ant from M. compactus . Also, unlike M. compactus , the eye of the minor worker is placed anteriorly on head capsule and is moderate in size (in profile, eye length ≈ 0.25 × length of side of head capsule). Melophorus postlei can be distinguished from its near relative, M. mjobergi , in that the appressed setae in all workers is fine and forms pubescence that largely obscures the underlying cuticle, which is matt in appearance.

Minor worker description.

Head. Head square; posterior margin of head strongly convex; frons matt or with weak sheen, microreticulate or microreticulate-shagreenate; frons consisting of appressed pubescence, with many short, unmodified, erect 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; 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; clypeal psammophore set at or above midpoint of clypeus; 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 matt or with weak sheen and microreticulate throughout; anterior mesosoma in profile smoothly rounded anteriad, thereafter pronotum and whole of mesonotum flattened and on same plane as propodeum; appearance of erect pronotal setae short, (i.e., longest erect setae shorter than length of eye) and unmodified; in profile, metanotal groove a weak or vestigial furrow; propodeum shining and microreticulate, or matt or with a weak sheen 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 setulae long and closely aligned, creating pubescence; propodeal spiracle situated on or beside declivitous face of propodeum, and longer (length ≥ 0.50 × height of propodeum). Petiole. In profile, petiolar node squamiform; in full-face view, shape of petiolar node tapered with blunt vertex; node shining and distinctly 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 brown to chocolate (gaster may be darker than foreparts).

Major worker description.

Head. Head quadrate (i.e., heart-shaped); posterior margin of head planar or weakly concave; cuticle of frons matt or with weak sheen, microreticulate; pilosity of frons a mixture of many short, erect, bristly setae interspersed with regularly spaced appressed setae. Eye moderate (eye length 0.20-0.49 length of head capsule); in full-face view, eyes set at about 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 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. Four 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 matt or with weak sheen and microreticulate throughout; anterior mesosoma in profile gently sinuous after initial steep pronotal incline; 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 a weak sheen and microreticulate; propodeum smoothly rounded or with indistinct angle; propodeal dorsum and declivity confluent; erect propodeal setae present and abundant (at least a dozen); appressed propodeal setae long and closely aligned, creating 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 tapered with blunt vertex; node shining and distinctly microreticulate. Gaster. Gaster weakly shining with indistinct shagreenation; pilosity of first gastral tergite consisting of a mixture of curved, erect and semi-erect setae and decumbent setae that form a variable pubescence. General characters. Colour uniformly reddish-brown.

Measurements.

Worker (n = 6): CI 87-114; EI 17-33; EL 0.15-0.23; HL 0.53-1.16; HW 0.46-1.33; ML 0.73-1.34; MTL 0.47-0.75; PpH 0.08-0.15; PpL 0.31-0.57; SI 61-144; SL 0.66-0.81.

Comments.

This small, neat Melophorus can be recognized by its thick pubescence, which obscures the underlying cuticle on the mesopleuron and forms a thatch on the first gastral tergite. Most Collections come from the NT, but the ant also occurs in the Kimberley and northern goldfields regions of WA and (in all probability) in far northern QLD. Sequencing data for two specimens confirm their sister relationship to M. mjobergi , which they very closely resemble. A mallee habitat 'on sand’ is the only ecological note from labels for this species.

Etymology.

After Dr. Tony Postle; noun in the genitive case.