Melophorus paramorphomenus 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 : 252-254

Melophorus paramorphomenus Heterick, Castalanelli & Shattuck sp. n.

Types.

Holotype minor worker (bottom ant) from Tropicana Minesite 29°15'40"S, 124°35'50"E, Western Australia, January 2009, J. Summerhayes, pitfall trap: Casuarina C1:4 [JDM32-004561] (WAM). Paratypes: 2 major workers on same pin with same details as holotype (WAM); 2 minor workers and queen from 12 km N of Billabong RH 26°44'S, 114°35'E, 11 December 2001, Heterick, B.E., Light scrub, red soil, am [JDM32-001988] (ANIC); minor worker from Barrow Island 20°49'43"S, 115°26'36"E, Western Australia, 17 May 2005, S. Callan, All 5 day pitfalls, R2 105 Pit 09 [JDM32-001989] (WAM).

Other material examined.

Western Australia: Barrow Island (Gunawardene, N. / Taylor, C. [M313]),

Diagnosis.

Melophorus paramorphomenus 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. Melophorus paramorphomenus cannot be confused with any other Melophorus except perhaps M. cuneatus , which, however, has the typical features of the M. biroi species-complex. The worker thorax possesses an apparent metanotum that is confluent with the mesonotum, and often extends over the propodeum. The metanotal suture is obsolete, its position indicated only by a superficial, transverse furrow (more pronounced in the major worker), the propodeum is reduced in size and wedge-shaped, with the narrow end of the wedge often under a fold of the metanotum and, finally, the metathoracic spiracle is lateral and situated within the metanotal sector

Minor worker description.

Head. Head square; posterior margin of head 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 at about midpoint of head capsule; in profile, set anteriad 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 straight; 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 shining and microreticulate, microreticulation reduced on humeri; anterior mesosoma in profile rounded anteriad, thereafter pronotum and whole of mesonotum flattened and on a higher plane than propodeum; appearance of erect pronotal setae short, (i.e., longest erect setae shorter than length of eye) and unmodified, or erect pronotal setae absent; in profile, metanotal groove absent; propodeum shining and finely striolate and microreticulate; propodeum wedge-shaped, tapering dorsad; length ratio of propodeal dorsum to its declivity not applicable, propodeal dorsum reduced to a narrow sliver; erect propodeal setae always absent; appressed propodeal setulae sparse or absent, if present then not regularly spaced; 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 distinctly shagreenate-microreticulate. Gaster. Gaster weakly shining with indistinct shagreenation; 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 dark ochre or orange tan, gaster brown.

Major worker description.

Head. Head square, or rectangular; posterior margin of head weakly convex; cuticle of frons shining and smooth except for piliferous pits; pilosity of frons a mixture of a few well-spaced, erect setae interspersed with appressed setae only. 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 straight in front of antennal insertion. Anterior clypeal margin straight; clypeal psammophore set at or above midpoint of clypeus; palp formula 6,4. Four mandibular teeth in major worker-5; 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 approximately aligned vertically or weakly oblique. Mesosoma. Integument of pronotum, mesonotum and mesopleuron shining with indistinct microsculpture that is most pronounced on lower surfaces; anterior mesosoma in profile steeply rounded anteriad, thereafter pronotum and whole of mesonotum flattened and on a higher plane than propodeum; erect pronotal setae short, (i.e., shorter than length of eye) and unmodified; in profile, metanotal groove a weak furrow; propodeum shining, with multiple hair like striolae; propodeum wedge-shaped, tapering dorsad; length ratio of propodeal dorsum to its declivity not applicable, propodeal dorsum reduced to a narrow sliver; erect propodeal setae absent; appressed propodeal setae sparse or absent, if present then not regularly spaced; 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 microreticulation anteriad. Gaster. Gaster shining with superficial microreticulation; pilosity of first gastral tergite consisting of thick, often distally flattened, erect setae over well-spaced, short, appressed setae. General characters. Colour orange tan with brown gaster.

Measurements.

Worker (n = 4): CI 103-120; EI 20-29; EL 0.17-0.27; HL 0.58-1.12; HW0.60-1.35; ML 0.84-1.45; MTL 0.51-0.87; PpH 0.05-0.04; PpL 0.27-0.47; SI 75-121; SL 0.73-1.01.

Comments.

The peculiarly developed metanotum, under which the propodeum is squeezed, distinguishes this ant from all others. Melophorus cuneatus , in the M. ludius complex, bears a superficial resemblance, but here the propodeum projects to the dorsum of the trunk as a wedge: that ant also possesses the diagnostic characters of its species complex (posteriorly placed clypeal psammophore, etc.). Andersen (2007), who erroneously places this species (and M. cuneatus ?) in the M. mjobergi complex ( ‘group’), comments on its resemblance to Notoncus enormis . The ant is known only from WA where it is found from about Kalbarri to Barrow Island. One inland sample has been collected at Tropicana Minesite, east of Laverton. Attempts to sequence pitfall trap material from Barrow Island have been unsuccessful, probably because of collection into diluted alcohol. The principal author of this revision has collected the species from a nest in red soil 12 km N of Billabong Station in the Midwest, but regrettably (as is the case with many other Melophorus ) other data are lacking.

Etymology.

Greek paramorphos ('change of physical shape’) plus Latinized Greek menus (Greek menos ‘spirit’ or ‘force’) referring to the odd appearance of the mesosoma; adjective in the nominative case.