Promyopias Santschi

Schmidt, C. A. & Shattuck, S. O., 2014, The Higher Classification of the Ant Subfamily Ponerinae (Hymenoptera: Formicidae), with a Review of Ponerine Ecology and Behavior, Zootaxa 3817 (1), pp. 1-242 : 129-131

Promyopias Santschi

Fig. 24

Promyopias Santschi, 1914: 323 (as subgenus of Myopias ). Type-species: Myopias (Promyopias) silvestrii Santschi, 1914: 324 ; by monotypy. Bolton & Fisher, 2008c: 28 ( Promyopias revived status as genus).

Promyopias is a monotypic genus restricted to western Africa. Nothing definite is known about its habits, but it is presumably hypogeic and may be a termite specialist.

Diagnosis. 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).

Synoptic description. Worker. 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.

Queen. Similar to worker but slightly larger, winged and with compound eyes and ocelli ( Bolton & Fisher, 2008c).

Male. Unknown.

Larva. Not described.

Geographic distribution. Promyopias is known only from a handful of collections from western Africa ( Bolton & Fisher, 2008c) .

Ecology and behavior. 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.

Phylogenetic and taxonomic considerations. Promyopias was originally described by Santschi (1914) as a subgenus of Myopias , based on similar mandibular and clypeal structure. Since that time the genus has had a complicated taxonomic history. Emery (1915) gave Promyopias full generic status, but Wheeler (1922b) considered it a subgenus of Pseudoponera . Wheeler’s association of Promyopias with Pseudoponera was apparently based on similarities in the mandibles and legs, though true Pseudoponera lacks the characters referred to by Wheeler, and we can only presume that he was referencing Pseudoponera amblyops (now Buniapone amblyops ). Santschi (1924) revived Promyopias to full genus status and placed it in subtribe Plectroctenini , but it was later synonymized under Centromyrmex due to the shared presence of spinose setae on the legs ( Brown, 1973; Bolton & Fisher, 2008c).

In their revision of African Centromyrmex, Bolton & Fisher (2008c) revived Promyopias once again to generic status, based on the unique structure of its helcium and the absence of the apomorphic metapleural gland orifice structure characteristic of Centromyrmex . Bolton & Fisher did note the multiple similarities between the genera, such as the eyeless condition of the workers, the spinose legs, and the high helcium, and suggested that these characters may be synapomorphic for these genera (along with Feroponera ).

However, recent preliminary molecular results (P.S. Ward, pers. comm.) suggest that Promyopias belongs to the Odontomachus group and is only distantly related to Centromyrmex . These results suggest that the similarities noted above are convergent rather than being apomorphic. Additional study will be required to clarify the placement of this genus within the subfamily Ponerinae .

Wheeler (1922b) apparently believed that Promyopias was closely related to Buniapone amblyops . These taxa share a number of morphological apomorphies, including narrowed mandibles (though the details of mandibular structure differ between them), a median clypeal projection, moderately large frontal lobes, basally flattened scapes, absent or reduced eyes, reduced or vestigial metanotal groove, ovoid propodeal spiracle, a high helcium, and spinose setae on the mesotibiae and meso-/metabasitarsi. Most of these morphological apomorphies are adaptations to a hypogeic lifestyle, and may have been convergently evolved by these genera. Both genera also have cuticular flaps at the metapleural gland orifice, though the details of this character differ between the genera: in Buniapone the metapleural gland orifice has two flaps, one anterior and one posterior to the orifice, while in Promyopias the flap is lateral and shields the orifice (B. Bolton, pers. comm.).

Figures

FIGURE 24. Worker caste of Promyopias silvestrii: lateral and dorsal view of body and full-face view of head (CASENT0178751, April Nobile and www.antweb.org); world distribution of Promyopias.