Promyopias

A monotypic genus that is only known from less than a dozen specimens of Promyopias silvestrii.

Identification
The morphology of the mandible is unique and readily separates silvestrii from other Ponerinae.

Schmidt and Shattuck (2014) - Workers of Promyopias can be identified by the following unique combination of characters: mandibles narrow and curved, anterior margin of clypeus with a blunt medial projection, eyes absent, metapleural gland orifice shielded laterally by a cuticular flap, traction setae present on mesotibiae and meso-/metabasitarsi, and petiole articulating near the midheight of the first gastral segment. The flap lateral to the metapleural gland orifice is autapomorphic. Promyopias workers may be confused with those of Centromyrmex, Buniapone, or Feroponera, as all four genera share traction setae on the legs, a relatively high helcium, and absent or tiny (in Buniapone) eyes. None of these other genera have similarly narrow and curved mandibles, however, and only Buniapone has a medial clypeal projection. Promyopias may also be confused with Myopias, but Myopias lacks traction setae on the legs, usually has eyes, and has a low helcium (among many other differences).

Biology
Bolton & Fisher (2008) - The only known species in the genus, Promyopias silvestrii is an uncommon but widely distributed species. Its diet, presumably termites but not actually demonstrated, may be more restricted or specialised than in Centromyrmex.

Schmidt and Shattuck (2014) - Nothing is known about the habits of Promyopias, though based on its morphological characteristics it is undoubtedly hypogeic. Bolton & Fisher (2008c) suggest that it most likely feeds on termites, though this has never been observed. Their hypothesis is apparently based on a presumed close relationship with Centromyrmex, which is a termite specialist. However, the mandibular and clypeal structure of Promyopias is much more similar to that of Myopias, Plectroctena, Leptogenys, and Psalidomyrmex, which are to large degrees specialist predators of millipedes (Myopias, Plectroctena), isopods ( Leptogenys), or earthworms (Psalidomyrmex). Long curved mandibles and medial clypeal projections are apparently favored for the capture of round prey (Déjean et al, 2001), and we hypothesize that Promyopias likewise feeds on some kind of hard round prey, most likely millipedes. On the other hand, both Plectroctena and Leptogenys include species known to feed on termites, so termite predation by Promyopias is not improbable.

Castes
Males have not been collected.

Nomenclature

 *  PROMYOPIAS [Ponerinae: Ponerini]
 * Promyopias Santschi, 1914d: 323 [as subgenus of Myopias]. Type-species: Myopias (Promyopias) silvestrii, by monotypy.
 * Promyopias subgenus of Myopias: Forel, 1917: 238.
 * Promyopias subgenus of Pseudoponera: Wheeler, W.M. 1922a: 649.
 * Promyopias raised to genus: Emery, 1915g: 26; Santschi, 1924a: 158; Brown, 1963: 10.
 * Promyopias junior synonym of Centromyrmex: Bolton, 1994: 164.
 * Promyopias revived status as genus: Bolton & Fisher, 2008c: 28.

Worker
Schmidt and Shattuck (2014) - Medium-sized (TL 6.0–6.3 mm) ants with the standard characters of Ponerini. Mandibles long and narrow, with at most a few small teeth and with a faint basal groove. Anterior margin of clypeus with a short blunt medial projection. Frontal lobes moderately large. Scapes moderately flattened. Eyes absent. Metanotal groove absent to distinct dorsally. Propodeum moderately narrowed dorsally. Propodeal spiracles ovoid. Metapleural gland orifice shielded laterally by a cuticular flap. Mesotibiae and meso-/metabasitarsi armed with stout traction setae. Metatibial spur formula (1s, 1p). Petiole nodiform, becoming wider posteriorly. Helcium projecting from near midheight of anterior face of A3. Gaster with a slight girdling constriction between A3 and A4. Head and body lightly sculptured (variously punctate, striate or smooth), with scattered pilosity and pubescence. Color dark orange. See Bolton & Fisher (2008c) for a more detailed description of worker structure, including a description of the lone autapomorphy of the genus: the unique shape of the prora.

Worker and Queen
Bolton and Fisher (2008) - A monotypic Afrotropical genus.


 * 1) Mandible elongate and narrow (MI 55–60 in worker). Apex of mandible armed with a short vertical series of 3–4 small teeth (may be worn and indistinct). Apical half of inner margin of mandible concave. Basal angle of mandible at about the midlength of the inner margin (where a small tooth is present) and proximal of this the long basal margin is shallowly convex. A weak basal groove present but without a dorsal longitudinal groove and without a basal pit.
 * 2) Palp formula 4,4.
 * 3) Median portion of clypeus projects slightly anteriorly, its anterior margin transverse.
 * 4) Frontal lobes with their anterior margin close to, but not overhanging, the anterior clypeal margin; in full-face view the distance from the most anterior point of a frontal lobe to the anterior clypeal margin is about equal to the basal width of the scape.
 * 5) Eyes absent in worker, present in queen.
 * 6) Antenna with 12 segments; scape somewhat dorsoventrally flattened; funiculus gradually incrassate towards the apex but without a strongly differentiated club.
 * 7) Frontal groove on mid-dorsum of head extends far posterior of the terminus of the frontal lobes.
 * 8) Pronotum bluntly and obtusely marginate anteriorly and laterally.
 * 9) Mesopleuron without a transverse suture that divides the sclerite into anepisternum and katepisternum.
 * 10) Metanotal groove (worker only) vestigial to moderately developed in dorsal view; in profile the propodeum continues the line of the mesonotum.
 * 11) Orifice of metapleural gland a posteriorly directed curved slit that is shielded from lateral view by a small lobe of cuticle, the orifice about level with the upper portion of the propodeal lobe.
 * 12) Metasternal process present as a pair of distinctly separated triangular long teeth that are slightly divergent and slightly curved posteriorly; metasternal pit is between the teeth.
 * 13) Propodeum unarmed, weakly bilaterally compressed in dorsal view so that propodeal dorsum is narrower than mesonotum.
 * 14) Propodeal spiracle broadly elliptical, almost round, low on the side and at about the midlength of the sclerite, abutting the metapleural gland bulla.
 * 15) Propodeal lobes bluntly triangular and prominent.
 * 16) Procoxa not hypertrophied but larger than the mesocoxa and metacoxa.
 * 17) Mesotibia, mesobasitarsus and metabasitarsus with strongly sclerotised spiniform traction setae; such setae absent from metatibia.
 * 18) Mesotibia and metatibia each with two spurs, the anterior small and simple, the posterior larger and pectinate.
 * 19) Pretarsal claws small, simple.
 * 20) Petiole in profile without an anterior peduncle.
 * 21) Subpetiolar process low, anterior and roughly broadly triangular.
 * 22) Helcium located close to mid-height on anterior face of the first gastral segment (abdominal segment III).
 * 23) Prora a longitudinal, thick, bluntly convex crest that extends from just below the helcium almost to the apex of the first gastral sternite.
 * 24) Girdling constriction between presclerites and postsclerites of second gastral segment present but shallow.
 * 25) Stridulitrum absent.
 * 26) Queen only (dealate). Moderately large eyes and conspicuous ocelli present. Mesosoma with full complement of flight sclerites. Transverse suture absent from mesopleuron (as in worker).

Discussion of female characters

Apomorphic characters, in italics above, include 1, 4 and 23. Characters 1–25 together form an inclusive diagnosis that isolates Promyopias workers and queens from all other genera in the tribe.

1. Elongate narrow mandibles that are linear to curvilinear have evolved independently several times in Ponerini. Often the narrowed mandible is universal in a genus (e.g. Harpegnathos, Odontomachus, Anochetus, Plectroctena, Myopias, Boloponera) but sometimes it is developed in some species groups of a genus but not others (e.g. Leptogenys stuhlmanni group and Leptogenys maxillosa group, Neoponera agilis group). In each case the detailed mandibular morphology, while consistent within a group, differs from that of other groups, which strongly suggests separate evolutions. The structure in Promyopias shows equally elongate but discernible basal and apical sections that are still quite distinct as the inner margin of the apical section is concave while the basal section is convex; the detailed structure here is unique.

2. PF 4,4 is the plesiomorphic maximum count for workers and queens in tribe Ponerini (Brown, 1963; Bolton, 2003).

4. In the sequence Centromyrmex–Promyopias–Feroponera the anterior margins of the frontal lobes draw closer to the anterior clypeal margin. In the first the anterior margins of the frontal lobes are plesiomorphically well posterior of the anterior clypeal margin, in the second quite close and in the third slightly overhanging the clypeal margin.

5. The loss of eyes in the worker caste but not in queens is also characteristic of Centromyrmex: see discussion of potential genus group, below.

6. The scape is broad in dorsal view and somewhat dorsoventrally flattened, but by no means as strongy flattened in its basal half as in Centromyrmex.

10. A discernible metanotal groove, that runs uninterruptedly across the entire dorsum of the mesosoma in workers, is variably developed. In two specimens the groove was vestigial, in three moderate and in one quite distinct.

11. Orifice of the metapleural gland is located normally here, close to the posteroventral corner of the mesosoma.

12. A bidentate to bispinose metasternal process is usual in Ponerini.

17. The presence and distribution of spiniform setae is duplicated in Centromyrmex and Feroponera.

18. This distribution of tibial spurs is certainly plesiomorphic in Ponerini as a whole; it is the basal condition from which all tibial spur modifications within the tribe have been derived.

22. Position of the helcium is similar in Centromyrmex and Feroponera.

23. The development of the prora in Promyopias appears unique in Ponerini.