Promyopias silvestrii (Santschi)

Bolton, B. & Fisher, B. L., 2008, Afrotropical ants of the ponerine genera Centromyrmex Mayr, Promyopias Santschi gen. rev. and Feroponera gen. n., with a revised key to genera of African Ponerinae (Hymenoptera: Formicidae)., Zootaxa 1929, pp. 1-37 : 31-32

Promyopias silvestrii (Santschi) comb. rev.

(Figs 29-32)

Myopias (Promyopias) silvestrii Santschi , 1914: 324, fig. 10. Syntype workers, GUINEA: Mamou, 24.viii.1913 (F Silvestri) ( NHMB) [examined]. [Combination in Promyopias by Emery, 1915: 26; in Pseudoponera (Promyopias) by Wheeler, W.M. 1922: 779; in Promyopias by Brown, 1963: 10; in Centromyrmex by Bolton, 1995: 140.] Comb. rev.

Promyopias asili Crawley , 1916: 30, fig. Holotype queen, MALAWI: Mlanje, 15.xi.1913 (S.A. Neave) ( BMNH) [examined]. [Combination in Pseudoponera (Promyopias) by Wheeler, W.M. 1922: 779. Synonymy with silvestrii by Brown, 1963: 10.]

WORKER. TL 6.0-6.3, HL 1.05-1.16, HW 1.00-1.12, CI 95-99, ML 0.62-0.68, MI 55-61, SL 0.62-0.64, SI 57-62, PW 0.74-0.86, WL 1.78-1.90 (5 measured).

With characters of the genus and the following. Dorsum of head densely punctulate-costulate, the sculpture stops near the posterior margin so that the occipital surface is mostly smooth and shining. Ventral surface of head longitudinally striolate and with scattered small punctures. Head capsule deep, in profile the maximum depth about 0.75 x HL. Scapes and cephalic dorsum with dense long pubescence that may be elevated, but without long setae such as are present on the clypeus and inner mandibular margins. Pronotum bluntly and obtusely marginate anteriorly and laterally. Metanotal groove vestigial to distinct across the dorsum, not impressed in profile. Pronotal dorsum broadly and densely punctate except for the median strip, which is smooth. Punctate sculpture on mesonotum weaker and more widely spaced than on pronotum; on propodeal dorsum the punctures weaker still, very sparse and almost effaced posteriorly. Sides of mesosoma finely striolate everywhere, or at most with posterior portion of mesopleuron smooth. PW about 1.85 x the maximum width of the propodeal dorsum. Gastral tergites with scattered small punctures. Dorsal surfaces of body with conspicuous pubescence or very short standing hairs everywhere. Occasionally one or two longer setae may occur on the petiole and gastral tergites 1-3, but long conspicuous setae are mostly confined to the apical gastral segment and the gastral sternites.

QUEEN. TL 7.6, HL 1.14, HW 1.17, CI 103, OI 21, ML 0.72, MI 63, SL 0.68, SI 58, PW 0.97, WL 2.32. All main morphological characters of the worker are duplicated in the queen caste; see under diagnosis of the genus.

MALE: unknown.

An uncommon but widely distributed species. Its diet, presumably termites but not actually demonstrated, may be more restricted or specialised than in Centromyrmex . The morphology of the mandible is unique and immediately identifies silvestrii .

Material examined. Guinea: Mamou (F. Silvestri). Ivory Coast: For. de Teke, Anyama (T. Diomande); Lamto, Toumodi (J. Levieux); Goudi (J. Levieux). Cameroun: Prov. Sud-Ouest, Bimbia Forest, ESE Limbe (B.L. Fisher). Angola: S. Rob't Williams (Ross & Lorenzen). Malawi: Mlanje (S.A. Neave)

Appendix 1. Is there a Centromyrmex genus group?

The three characters discussed below may diagnose a Centromyrmex genus group within tribe Ponerini (sensu Bolton, 2003), which contains the three genera Centromyrmex , Promyopias and Feroponera . At present none of these characters have been proven to be synapomorphies or independently evolved, but they are universal in these genera. The status of the characters must await a more comprehensive survey of the entire tribe.

1 Presence of strongly sclerotised, stoutly spiniform traction setae on the metabasitarsus in workers and queens.

Only these three genera in Ponerini have stout spiniform traction setae on the metabasitarsus in the female castes. Similar setae, usually more strongly developed, are also universal on the mesotibia and mesobasitarsus of all three genera. Elsewhere in the tribe such setae also occur on the mesotibia, and sometimes also the mesobasitarsus in Cryptopone , though they are never as strongly developed; and on the mesotibia of a single species of the Plectroctena genus group, Psalidomyrmex foveolatus . However, none of these exhibit such setae on the metabasitarsus.

Ps. foveolatus acquired mesotibial spiniform setae independently, as the Plectroctena genus group ( Plectroctena (16 species), Loboponera (9 species) and Psalidomyrmex (6 species)) has a unique set of apomorphies(Bolton & Brown, 2002) not exhibited by the Centromyrmex group. No other member of the Plectroctena group has spiniform traction setae on any of the legs.

In Cryptopone (22 species) the traction setae are more feebly developed, are restricted to the mid-leg (usually just to the mesotibia), and are always absent from the metabasitarsus. In addition, Cryptopone species differ from the genera treated here as all have a basal mandibular pit present and a palp formula of 2,2 at maximum(Brown, 1963). It therefore seems reasonable to assume that spiniform traction setae evolved independently in Cryptopone .

2 Helcium projects from near midheight of anterior face of first gastral segment in workers and queens. In Ponerini the helcium is usually attached very low on the anterior face of the first gastral segment, and the first gastal tergite forms a relatively long vertical face above it. Exceptions to this, in addition to the Centromyrmex group, where the helcium is relatively high and the anterior face of the first gastral tergite is shortened, occur in Harpegnathos , various Cryptopone species and the monotypic genera Dolioponera and Boloponera . Fisher (2006) speculates that the last two together may constitute the sister-group of the Plectroctena group of genera. Harpegnathos , based on its unique morphology, cannot be considered as close to Centromyrmex and its allies. Cryptopone , despite its differences from the potential group under discussion here, may be related but the possibility awaits investigation.

3 Eyes absent in worker caste.

The absence of eyes in the worker caste may be a synapomorphy of the group. In most genera of Ponerini eyes are usually present, even if often very reduced, but there are some where eyes are absent in some species but present in others (e.g. Hypoponera , Plectroctena , Cryptopone , Pachycondyla , Myopias ), and in Dolioponera larger workers have eyes while smaller ones are eyeless (Fisher, 2006). Loss of eyes may therefore be apomorphic within species, in individual species in a genus, or in a group of species within a genus, but it is worth noting that universal loss appears only to have happened in the three genera revised here.