Neoponera Emery

Field: Agricultural and Biological Sciences (Life Sciences)

Neoponera Emery Fig. 30 Neoponera Emery, 1901: 43 (as genus). Type-species: Formica villosa Fabricius, 1804: 409; by original designation. Gen. rev. Eumecopone Forel, 1901b: 335 (as subgenus of Neoponera). Type-species: Neoponera (Eumecopone) agilis Forel, 1901b: 336; by monotypy. Brown, 1973: 180 (Eumecopone as provisional junior synonym of Neoponera). Termitopone Wheeler, W.M., 1936: 159 (as genus). Type-species: Ponera laevigata Smith, F., 1858: 98; by original designation. Termitopone as junior synonym of Neoponera: Syn. nov. Syntermitopone Wheeler, W.M., 1936: 169 (as subgenus of Termitopone). Type-species: Ponera commutata Roger, 1860: 311; by original designation. Syntermitopone as junior synonym of Neoponera: Syn. nov. Neoponera is a large (54 described species) Neotropical genus, and is one of the most morphologically and behaviorally diverse of all ponerine genera. Many Neoponera are arboreal, and some species are specialized mass raiders of termites. Diagnosis. Neoponera is morphologically diverse. Its workers can be most readily identified by the following combination of characters: eyes relatively large and located at or near the midline of the head, metapleural gland orifice with a U-shaped posterior cuticular lip and lateral groove, arolia prominent, stridulitrum present on pretergite of A4, and hypopygium without a row of stout spines on either side of the sting. Many Neoponera also have distinct preocular carinae. Members of Neoponera are superficially most similar to Pachycondyla, Mayaponera, Mesoponera, and perhaps Megaponera. Neoponera workers differ most obviously from those of Pachycondyla in having prominent arolia, a stridulitrum on the pretergite of A4, and an unarmed hypopygium, and differ from those of Mayaponera in having slit-shaped propodeal spiracles and at most only a shallowly impressed metanotal groove. Neoponera species with round propodeal spiracles (some members of the N. emiliae group) can be separated from Mayaponera by the triangular-shaped metasternal processes (the processes are narrow and fanglike in Mayaponera). Both Mesoponera and Megaponera lack the complex metapleural gland orifice and prominent arolia of Neoponera. Synoptic description. Worker. Medium to large (TL 6.5–19 mm) slender ants with the standard characters of Ponerini. Usually monomorphic, but size polymorphic in N. laevigata, N. marginata, and N. luteola. Mandibles triangular, with numerous teeth on the masticatory margins and often with a faint basal groove. Anterior clypeal margin convex, sometimes emarginate or coming to a point medially. Frontal lobes of moderate size. Preocular carinae present (Neoponera s.s.) or absent (“ Termitopone ” and relatives). Eyes large to very large, placed at or anterior to head midline. Pronotum often with sharp humeral margins (rounded in “ Termitopone ” and relatives). Mesopleuron often divided by a transverse groove, but sometimes undivided. Metanotal groove sometimes shallowly impressed but usually reduced to a simple suture. Propodeum moderately narrowed dorsally and often with shallowly ridged posterior margins. Propodeal spiracles slit-shaped in most species, round in a few (P. concava, P. emiliae, P. schultzi, P. venusta). Metapleural gland orifice with a U-shaped posterior cuticular lip and a lateral groove. Metatibial spur formula (1s, 1p). Arolia prominent. Petiole nodiform but highly variable, in Neoponera s.s. the node usually with a vertical or sloped anterior face and a sloping posterodorsal face, the two faces meeting along a sharp edge; the node is more rounded in “ Termitopone ” and its relatives. Gaster with a strong to moderate girdling constriction between pre- and postsclerites of A4. Stridulitrum present on pretergite of A4. Head and body usually finely punctate, sometimes striate, pruinose, or smooth and shiny (” Termitopone ”). Head and body with sparse to scattered pilosity, and with absent (” Termitopone ”) to abundant pubescence. Color variable, orange to black. Queen. Very similar to worker but winged, slightly larger, and with ocelli and the modifications of the mesosoma typical of alate ponerine queens. Male. See descriptions for individual species in Forel (1899), Santschi (1921, 1923), Wheeler (1925, 1936), Borgmeier (1959) and Mackay & Mackay (2010). Larva. Described for individual species by Wheeler & Wheeler (1952, 1971a, 1974), Petralia & Vinson (1980) and Mackay & Mackay (2010). Geographic distribution. Neoponera is a strictly Neotropical genus and ranges from southern Texas and northern Mexico to northern Argentina and southern Brazil, with some species spanning virtually that entire range and others with more restricted distributions (Emery, 1911; Longino, 2013; Mackay & Mackay, 2010). Ecology and behavior. Neoponera is among the most behaviorally diverse of all ponerine genera. While relatively little is known about most members of the genus, certain species groups (especially the N. apicalis, N. laevigata, and N. villosa groups) have been heavily studied and have become model systems for studies of social and foraging behavior. Phylogenetic evidence suggests that the ancestral Neoponera was an epigeic generalist predator and scavenger that foraged on the ground (see discussion of phylogenetic relationships within Neoponera, below). This is still apparently the pattern followed by those Neoponera species formerly placed in Mesoponera (such as N. aenescens; Longino, 2013), as well as members of the N. apicalis species group (see below). From this ancestral condition two major deviations occurred: the ancestor of the N. laevigata group became a specialized mass raider of termites, while the ancestor of most members of Neoponera (s.s.) took the unusual step among ponerines of becoming arboreal. Colonies of most Neoponera species are small, with typically fewer than 200 workers (e.g., N. carinulata, N. crenata, N. lineaticeps, and N. unidentata: Longino, 2013; N. apicalis species group: Fresneau, 1985; Fresneau & Dupuy, 1988; Düssmann et al., 1996; Gobin et al., 2003a; N. villosa species group: D’Ettorre et al., 2006). Exceptions include N. goeldii, whose colonies can have at least 500 workers (Denis et al., 2007), the N. laevigata species group, which have colony sizes of up to at least 1,800 workers (Leal & Oliveira, 1995; Longino, 2013), and N. luteola, which reportedly has colonies with tens or hundreds of thousands of workers (Yu & Davidson, 1997). An interesting behavior observed in some Neoponera species is the collection of drops of water or honeydew between the mandibles (e.g., in N. apicalis: Fresneau & Dupuy, 1988). N. villosa workers collect drops of liquid between their mandibles and act as “social buckets” by distributing the liquid to their nestmates (Déjean & Corbara, 1990b; Hölldobler & Wilson, 1990; Paul & Roces, 2003); some of the liquid may be used to control nest humidity (Hölldobler & Wilson, 1990). The ants use their mandibles as an external crop, to compensate for their lack of proper structures for internal liquid storage. Among those Neoponera species that are terrestrial generalist predators and scavengers, only the members of the N. apicalis species group (N. apicalis, N obscuricornis, and N. verenae) have been heavily studied, though they are behaviorally quite derived and should not necessarily be considered typical of terrestrial generalist Neoponera. The N. apicalis species group was revised by Wild (2005), who provided a good summary of the habits of these species and noted that most published studies on N. obscuricornis actually involved N. verenae. Individual workers forage diurnally among leaf litter or on low vegetation for live and dead insects, vertebrate carcasses, fruit, and nectar sources, and look and behave similarly to pompilid wasps (Fresneau, 1985; Fresneau & Dupuy, 1988; Wild, 2002; Sujii et al., 2004; Longino, 2013). The foraging behavior of N. apicalis was studied in detail by Fresneau (1985), and modeled by Goss et al. (1989). Computer scientists have used models of N. apicalis foraging behavior to develop highly efficient search algorithms for complex problems in computer science (e.g. Monmarché et al., 2000; Wang & Ip, 2005; Admane et al., 2006; Luh & Lin, 2008). Duelli & Duelli-Klein (1976) found that workers of P. verenae can navigate using patterns of polarization of sunlight. Members of the N. apicalis species group construct small nests in rotting wood or soil (Traniello & Hölldobler, 1984; Fresneau & Dupuy, 1988; Pezon et al., 2005; Wild, 2002, 2005). Colonies emigrate frequently to new nest sites via tandem running (Fresneau, 1985; Pezon et al., 2005), which is mediated by a pheromone produced in the pygidial gland (studied in N. verenae: Traniello & Hölldobler, 1984). The reproductive and social behaviors of the N. apicalis group have been extensively studied. Colonies are facultatively polygynous (N. apicalis: Fresneau & Dupuy, 1988; N. verenae: Traniello & Hölldobler, 1984) and may include intercaste queens which both mate and lay eggs (N. verenae: Düssman et al., 1996). Workers apparently are unable to mate and in queenright colonies will usually only lay trophic eggs (queens largely suppress worker reproduction), but in queenless nests workers will lay haploid eggs (Düssman et al., 1996; Dietemann & Peeters, 2000). Workers form dominance hierarchies in both queenright and queenless colonies, with the highest ranked individuals dominating the egg laying (Oliveira & Hölldobler, 1990, 1991; Düssman et al., 1996; Gobin et al., 2003a). Gobin et al. (2003a) found that such dominance interactions impose a significant energetic cost on the colony. Ovarian development in N. verenae workers and queens is related to their social status (Fresneau, 1984). The division of labor among N. apicalis workers is similar to that of most ants, with the exception that queens engage in colony work to an unusually high degree (Fresneau & Dupuy, 1988). Several studies have examined the struct