Rasopone, Schmidt & Shattuck, 2014

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 : 208-210

Rasopone gen. nov.

Fig. 50

Type-species: Ponera ferruginea Smith, F. 1858b: 100 ; by present designation.

Rasopone is small genus of Central and South America ants known from 11 species. They are found in a wide range of habitats but are most common in rainforests where they forage in leaf litter and rotten wood.

Etymology. Rasopone is based on the geographic region of the New World where these ants occur (from the Ancient Egyptian “rsw”, “south wind”) combined with the suffix “-pone”, derived from the subfamily name Ponerinae .

Diagnosis. Workers of Rasopone lack obvious autapomorphies and are superficially similar to those of a number of other genera, including Austroponera , Hypoponera , Neoponera and Pseudoponera . Separation from these and other genera of the Ponerinae is based on the following set of characters: eyes present, mandibles relatively long, mandibular pit or groove absent, mesosomal profile nearly continuous, the metanotal groove shallow or absent, metapleural gland orifice without a posterior U-shaped cuticular lip, propodeal spiracle round or ovoid, mesotibiae dorsally without abundant stout traction setae, ventral apex of the metatibia with both a large pectinate spur and a smaller simple spur, fenestra absent from the petiolar process, prora present on anterior margin of first gastral sternite, and stridulatory organ absent from A4 pretergite. While similar overall, Rasopone and Neoponera belong to different genus groups and can be separated by the configuration of the metapleural gland opening. Hypoponera , while also somewhat similar, has only a single metatibial spur while two are present in Rasopone . Separation from Pseudoponera is based on the lack of a basal mandibular pit or groove and the presence of a round or ovoid propodeal spiracle. And the Australian and New Zealand genus Austroponera differs in possessing a stridulatory organ on A4 and in having a differently configured clypeus.

Synoptic description. Worker. Medium- to large-sized (TL 4–12 mm) ants with the standard characters of Ponerini .

Mandibles triangular, with roughly seven to twelve teeth, often variable size, and without a basal pit or groove. Anterior margin of clypeus variable, broadly convex or centrally concave, sometimes with a medially tooth. Frontal lobes moderately large and closely approximated. Eyes small to moderately large, located far anterior on sides of head. Mesopleuron generally entire but sometimes divided by a weak transverse impression. Metanotal groove reduced to a suture or shallow angle. Propodeum not narrowing dorsally. Metapleural gland orifice without a posterior U-shaped cuticular lip. Propodeal spiracles round or ovoid. Metatibial spur formula (1s, 1p). Petiole squamiform. Gaster with a girdling constriction between pre- and postsclerites of A4. Head and body finely punctate, sometimes with light striations on the sides of the mesosoma, and with sparse to abundant pilosity and often dense pubescence. Color variable, ferrugineous to dark brown-black.

Queen. Similar to worker but slightly larger, alate, with ocelli and larger compound eyes, and with the modifications of the thoracic sclerites that are typical of alate ponerine queens.

Male. See descriptions by Mackay & Mackay (2010) for several of the species placed here.

Larva. Described for R. ferruginea ( Wheeler & Wheeler, 1976) and R. pergandei ( Wheeler & Wheeler, 1974) .

Geographic distribution. Rasopone is restricted to Central and South America.

Ecology and behavior. While these ants are most abundant in forested habitats, they occur in a wide range of habitats, including open disturbed grassy areas, cacao and coffee plantations, mixed dry oak forest, upper montane oak forest, rocky tropical canyons, second growth rainforest, tropical montane evergreen forest, wet montane forest, primary rainforest, and cloud forest ( Mackay & Mackay, 2010). R. ferruginea has been collected in caves near the entrances ( Reddell & Cokendolpher, 2001). Workers forage in leaf litter and rotten wood and have been collected in subterranean traps baited with Vienna sausage; they are known to be attracted to carrion ( Mackay & Mackay, 2010). Most species nest in soil with some also nesting in rotten wood. Baena (1993) reported a specimen of R. conicula (listed as P. pergandei ) collected in a rotten log, and the type series of R. cernua was found in a log, suggesting that logs may be the normal nesting site for these species. Most flights of R. arhuaca occur in the middle of the summer ( Kaspari et al., 2001).

Phylogenetic and taxonomic considerations. None of the species treated here as belonging to Rasopone were included in Schmidt’s (2013) phylogeny and our analysis is based on morphology alone. They were examined in detail by Mackay & Mackay (2010) who placed them in two species complexes, the arhuaca species complex ( R. arhuaca , R. becculata , R. cernua , R. conicula , R. longidentata and R. pergandei ) and the ferruginea species complex ( R. breviscapa , R. ferruginea , R. lunaris , R. minuta and R. rupinicola ). Because all were considered by Mackay & Mackay (2010) to belong to Pachycondyla and the focus of their work was species-level identification, the relationships among these species and others in the subfamily were not discussed in detail but rather only in general terms. Further detailed study specifically aimed at elucidating the relationship of this group of species to the remainder of the Ponerinae will be required to fully understand the evolution of this genus.

Rasopone is morphologically very similar to species here placed in Austroponera and they share many characters. They differ in that Rasopone workers lack a stridulatory organ on A4 and in having a differently configured clypeus. These differences are subtle and it may be more appropriate to combine these two genera in the future when their true relationships are better understood. We are, however, proposing both as separate for the time being based on morphological (as outline above) and biogeographic considerations ( Rasopone is only known from Central and South America while Austroponera occurs in the Australian region).

Figures

FIGURE 50. Worker caste of Rasopone ferruginea: lateral and dorsal view of body and full-face view of head (CASENT0249143, Ryan Perry and www.antweb.org); world distribution of Rasopone.