Polyrhachis porcata species-group

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The Polyrhachis gravis species-group is comprised of species in the subgenus Aulacomyrma.




This group is characterized by the following: mesosomal margins poorly defined or completely absent. Pronotal humeri armed with broad-based teeth or short spines; pronotal lateral margins absent or extending posteriorly for only a short distance before merging with outermost dorsal striae and curving onto sides of pronotum without reaching promesonotal suture. Mesonotal-propodeal dorsum usually with only one or other marginate, or completely immarginate. Petiole scale-like with anterior and posterior faces convex and dorsal margin acute or blunt. Anterior face of first gastral segment distinctly concave in all species, except decora and its allies, where it is truncate or even convex. Within the group the species tend to polarise into four, rather intergrading, complexes, centering on excellens, porcata, geometrica and orokana. Species in the excellens complex are more similar to the dohrni-group species, featuring short and weak pronotal margins and only a weakly convex mesosomal dorsum. The sculpture of mesosoma consists of mostly longitudinal, relatively widely spaced striae of a “ploughed” appearance, as in excellens or maai. Species of the porcata complex tend to have the mesosomal dorsum, distinctly transversely convex, the pronotal dorsum completely immarginate, and the mesonotal-propodeal dorsum with one or the other marginate, as in porcata or monticola. The sculpture of the mesosomal dorsum consists mostly of longitudinal striae curved into various V- or U-shaped patterns, notably on the pronotum. The geometrica complex include species with a virtually immarginate mesosoma, both laterally and posteriorly, although in some species closely related to geometrica the outermost striae of the mesonotal dorsum form an ill-defined lateral margin. The pronotal humeri are armed with distinct, more-or-less isolated teeth or spines. The anterior face of the first gastral segment is only shallowly concave, as in geometrica or roomi, or simply convex as in decora or kokoda. The sculpture of the mesosomal dorsum is intricate with the striae forming transverse, V-, U- or semicircle-shaped patterns, giving the surface a characteristic “geometrical” appearance.

The two species comprising the orokana complex are in most aspects very similar to species of the geometrica complex. However, they differ by the presence of a very prominent transverse ridge on propodeum, separating the propodeal dorsum from the declivity and by the complete lack of lateral mesosomal margins.

The nomenclature section of the Aulacomyrma subgenus page also includes information about distinctions between this species-group and the Polyrhachis dohrni species-group.

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