Melophorus brevipalpus 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 : 283-286

Melophorus brevipalpus Heterick, Castalanelli & Shattuck sp. n.

Types.

Holotype minor worker (bottom ant) from Emu Camp, Victoria Desert, South Australia, 5 October 1976, P.J. M. Greenslade, (6) [ANIC32-066590] (ANIC), Paratypes: major worker on same pin and with same details as holotype (ANIC); minor and major worker from 50 km S of Coober Pedy 29.27S, 134.51E, South Australia, 2 October 1981, D. Davidson/S. Morton, 67a (ANIC); media and minor worker from Observatory Hill, Victoria Desert, South Australia, 7 October 1976, P.J. M. Greenslade, (5) (BMNH); 2 media workers from 10 km E of Mt Ive HS, Gawler Ranges, South Australia, 21-22 October 1980, P.J. M. Greenslade, 18) (MCZ); 2 major workers and a media worker from 10 km E of Mt Ive HS, Gawler Ranges, South Australia, 21-22 October 1980, P.J. M. Greenslade, B Se (SAM).

Other material examined.

South Australia: 10 km E Mt Ive Homestead, Gawler Ranges (Greenslade, P.J. M. ), 85 km W Mabel Creek (Greenslade, P.J. M. ), 85 km W Mabel Creek (Greenslade, P.J. M. ), Koonamore, Milang Conservation Park (Greenslade, P.J. M. ).

Diagnosis.

Melophorus brevipalpus 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. wheeleri species-complex because it agrees with the following apo morphies possessed by the complex: the minor worker often has more than five teeth, the largest major worker has a short, massive, elbowed mandible directed posteriad; in profile, the maxillary palps are short in the major and generally short in minor workers (in the minor worker, usually only attaining the neck sclerite at their maximum extent when the head is moderately inclined) and, in full-face view, the anterior margin of the clypeus in the large major worker is usually planar or weakly concave (variable in other subcastes but planar or narrowly protuberant anterior clypeal margins predominate). The reduced palps in M. brevipalpus (PF of 4,3; 3,3 and possibly 2,3 [undissected major worker]) only parallel the reduced palps in the unrelated and morphologically very different M. potteri species-group. These palps are extremely short and when they are directed posteriad do not reach the hypostomal border. This feature alone is sufficient to identify the species within the M. wheeleri complex.

Minor worker description.

Head. Head square; posterior margin of head planar or weakly convex; frons shining with superficial shagreenation or microreticulation only; 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 concave; frontal lobes straight in front of antennal insertion. Anteromedial clypeal margin straight; clypeal psammophore set at or above midpoint of clypeus; palp formula variably reduced (4,3 or 3,3). Five to six mandibular teeth in minor worker; mandibles triangular, weakly incurved; third mandibular tooth distinctly shorter than apical tooth, but equivalent in length to remaining teeth; masticatory margin of mandibles approximately vertical or weakly oblique. Mesosoma. Integument of pronotum, mesonotum and mesopleuron shining and microreticulate, microreticulation reduced on humeri; anterior mesosoma in profile broadly convex; erect pronotal setae absent; in profile, metanotal groove shallow, broadly V or U-shaped; propodeum shining and microreticulate; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity about 1:1; erect propodeal setae always 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; 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 short, inconspicuous, appressed setae, erect setae (present in at least some workers) confined to margin of sclerite. General characters. Colour of foreparts orange tan to brown, gaster blackish-brown to black.

Major worker description.

Head. Head horizontally rectangular, broader than wide; posterior margin of head planar or weakly concave; cuticle of frons shining and smooth except for piliferous pits; 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 curved inward in front of antennal insertion, or curved toward antennal insertion. Anterior clypeal margin broadly emarginate; clypeal psammophore set at or above midpoint of clypeus; palp formula variably reduced (4,3 or 3,3 or even 2,3).Five or six mandibular teeth in major worker; mandibles strongly incurved, apical sector weakly carinate or incompletely carinate; third mandibular tooth distinctly shorter than apical tooth, but equivalent in length to remaining teeth; masticatory margin of mandibles approximately aligned vertically or weakly oblique. Mesosoma. Integument of pronotum, mesonotum and mesopleuron shining with very superficial microreticulation, entire lower mesopleuron distinctly shagreenate; anterior mesosoma in profile broadly convex; erect pronotal setae short, (i.e., shorter than length of eye) and unmodified, or erect pronotal setae absent; in profile, metanotal groove shallow, indicated mainly by an angle and metathoracic spiracles; propodeum shining and microreticulate; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity between 1:1 and 1:2; erect propodeal setae variable in number, may be absent; appressed propodeal setae short, separated by more than own length and inconspicuous; 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, or tapered with squared-off vertex; node shining and smooth with vestigial microreticulation anteriad. Gaster. Gaster shining, shagreenate ('LP record’ appearance); pilosity of first gastral tergite consisting of well-spaced, erect and semi-erect setae interspersed with regularly spaced appressed setae. General characters. Colour of foreparts orange tan (head of deeper hue), gaster dark brown.

Measurements.

Worker (n = 6): CI 112-118; EI 20-29; EL 0.20-0.26; HL 0.61-1.12; HW 0.68-1.31; ML 0.85-1.29; MTL 0.53-0.83; PpH 0.11-0.13; PpL 0.35-0.51; SI 68-92; SL 0.63-0.90.

Comments.

Because of its very short palps, which have an abbreviated number of segments, and its morphological resemblance to M. wheeleri , Melophorus brevipalpus cannot be mistaken for any other Melophorus . While a reduced PF is also found in several other species, including two in the M. potteri species-group, these latter taxa have a distinctive habitus. Melophorus brevipalpus has thus far only been recorded at a few localities in SA. No specimens were available for sequencing. One specimen was collected in a pitfall trap, but there are no other data. Nonetheless, given its apparent affinities with the M. wheeleri complex, we tentatively associate this species with a granivorous lifestyle.

Etymology.

Latin brevis ( ‘short’) plus palpus ( ‘stroking’/‘caress’; applied to the palps of an arthropod); noun in the nominative singular standing in apposition to the generic name.