Rhopalomastix Forel

Genus Rhopalomastix Forel

Rhopalomastix Forel, 1900: 24. Type-species: Rhopalomastix rothneyi, by monotypy Rhopalomastix in Myrmicinae, Solenopsidini: Wheeler, W.M., 1910: 140. Rhopalomastix in Myrmicinae, Melissotarsini: Emery, 1914: 40; Forel, 1917: 242; Emery, 1922: 118; Wheeler, W.M. 1922: 661. Rhopalomastix in Myrmicinae, Crematogastrini: Ward et al., 2015: 71, 77.

Diagnosis of genus. Worker. Total length approximately 1.59–2.62 mm, HL 0.39–0.58, HW 0.36–0.56. Worker monomorphic with variation in size. Head in full-face view subrectangular or subquadrate; frontal carina and antennal scrobe weak; frontal lobes touching or separated only by a narrow longitudinal impression. Median portion of anterior clypeal margin weakly convex anteriorly and projected forward slightly from lateral clypeal margin, lined with minute denticles. Mandible short, subtrapezoidal, its masticatory margin with a few teeth, usually one large apical tooth, a smaller pre-apical tooth, and 2-3 minute, reduced denticles. Antenna with 10 segments, antennal club 2-segmented; antennal scape short, extending a little beyond midlength of head when laid backwards; antennal funiculus flattened in appearance. Eye relatively large, with 5–6 ommatidia in the longest axis, located well in front of midlength of side of head. Mesosoma box-shaped; promesonotal suture absent dorsally; metanotal groove absent; propodeum unarmed; metapleural gland bulla large; propodeal lobe reduced and indistinct. Procoxa subtriangular and anteriorly expanded into smooth and rounded lobe. Fore- and hind femora extremely widened and flattened distally. Petiole nodiform, with relatively high node, anteroventrally with welldeveloped subpetiolar process, globular in dorsal view. Postpetiole much shorter than high, broadly attached to anteriormost portion of gaster. Gaster in dorsal view elliptical in shape, first gastral tergite much larger compared to the rest.

Queen. Differing from associated workers in the following characteristics: body slightly larger; eye very large in size (>100 ommatidia); ocelli present; promesonotal suture deeply impressed; metapleuron large, in profile view rounded subrectangular, with distinct metapleural furrow that is oblique and linear, directed posterodorsally. Sculpturing on head usually weaker than in worker. Clypeus usually with two pairs of erect hairs—one pair of setae on the median anterior clypeal margin, another pair of longer hairs closer to the posterior clypeal margin.

Male. Head including eye in full-face view rounded or broadly ovate. Eye extremely large (>100 ommatidia) and bulging; ocelli relatively larger than in queen. Mandible reduced and nub-like; clypeus in profile strongly projected from anterior margin of head. Ventrolateral corner of head roundly convex. Antenna 12-segmented, without obvious antennal club, scape very short. Mesosoma elongate, not box-shaped. Petiole sometimes similar to that in worker but relatively longer than high, anterior margin always longer than posterior, in dorsal view, petiole including anterior face subcylindrical. Subpetiolar process besides distal anteroventral point typically lighter in colour and more translucent than adjacent sclerites. Postpetiole relatively flat, broadly attached to anteriormost portion of gaster; gaster elliptical in dorsal view. Hairs on dorsum of mesosoma usually most abundant on mesoscutum, sparser or absent on mesoscutal disc and propodeum.