Odontoponera Mayr

Odontoponera Mayr

Fig. 20

Odontoponera Mayr, 1862: 713, 717 (as genus in Ponerinae [Poneridae]). Type-species: Ponera denticulata Smith, F., 1858: 91; by monotypy.

Odontoponera is a small genus with two species and 3 subspecies restricted to Southeast Asia, where it is one of the most commonly observed ants.

Diagnosis. Workers of Odontoponera are easily differentiated from other ponerines by their denticulate anterior clypeal margin, toothed pronotal margins, denticulate-emarginate petiolar scale and a small, ventrallydirected tooth at the apex of the hypopygium, all of which are autapomorphic within Ponerinae. The strong striate sculpturing of Odontoponera is also characteristic, though Diacamma, Ectomomyrmex and Paltothyreus also have striate sculpturing (these genera lack the other diagnostic characters of Odontoponera).

Synoptic description. Worker. Medium-sized (TL 9–12 mm; Bingham, 1903) ants with the standard characters of Ponerini. Mandibles short, triangular and massive, with a basal groove. Clypeus with a denticulate anterior margin. Eyes fairly small, placed anterior of head midline, with a subtle preocular carina (often difficult to distinguish from the striate sculpturing of the head). Pronotum with a short spine at each anterodorsal corner. Metanotal groove very shallowly impressed or reduced to a simple suture. Propodeum narrowed dorsally, the posterior margins with shallow denticulate ridges. Propodeal spiracle ovoid. Metatibial spur formula (1s, 1p). Petiole squamiform, with a sharp denticulate and emarginate dorsal margin. Gaster with only a weak girdling constriction between pre- and postsclerites of A4. Stridulitrum present on pretergite of A4. Head and mesosoma deeply striate, the gaster only lightly punctate. Head and body with scattered pilosity and only light pubescence. Color ferrugineous to black.

Queen. Similar to worker but larger (TL 11–13 mm; Bingham, 1903) and winged.

Male. See description in Smith (1858).

Larva. Described by Wheeler & Wheeler (1952).

Geographic distribution. Odontoponera is restricted to Southeast Asia, where its range stretches from India to the Philippines and from southern China to the Lesser Sunda Islands of southern Indonesia (Creighton, 1929).

Ecology and behavior. Virtually nothing is known about the social behavior of Odontoponera, but the genus has received some attention from ecologists due to its abundance. For example, Wheeler & Chapman (1925) noted the abundance of Odontoponera at a site in the Philippines, and it was common in a Bornean rainforest (Berghoff et al., 2003), was one of the dominant ants in a study in Vietnam (Eguchi et al., 2004), was the dominant groundnesting ant in a study in Thailand (Sitthicharoenchai & Chantarasawat, 2006), was one of the most abundant ants in a forest in southern China (Zhou et al., 2007), and one of us (CAS) frequently observed it in a rainforest in peninsular Malaysia. Levy (1996) reported a density of 3,000 nest entrances per hectare in a Bornean rainforest. Colonies have over 100 workers, and the polydomous subterranean nests are linked by interconnecting tunnels (Berghoff et al., 2003).

Odontoponera workers are predominantly epigeic foragers and are generalist predators and scavengers (Levy, 1996; Hashimoto et al, 1997; Berghoff et al., 2003; Pfeiffer et al., 2006; Zhou et al., 2007). Wheeler & Chapman (1925) noted that, in the Philippines, Odontoponera “is especially fond of termites and is often seen raiding their colonies.” Remarkably, Berghoff et al. (2003) observed that Odontoponera workers are effective at guarding their nest entrances from marauding Dorylus army ants and that the Odontoponera workers actually prey on the Dorylus. Ants and termites made up nearly half of the food items collected by O. transversa workers in the study by Levy (1996). Workers only forage within about a meter from the nest entrances (Eguchi et al., 2004).

Morgan et al. (1999, 2003) studied the mandibular gland and abdominal gland secretions of Odontoponera, and Leluk et al. (1989) examined the protein composition of Odontoponera venom.

Phylogenetic and taxonomic considerations. Odontoponera was erected by Mayr (1862) to house the single species Ponera denticulata F. Smith (now a junior synonym of O. transversa). The genus has experienced complete taxonomic stability at the genus level, as all subsequent authors have continued to treat it as a distinct genus.

We also consider Odontoponera to be distinct from other genera. Schmidt's (2013) molecular phylogeny of Ponerinae places Odontoponera with strong support within the Odontomachus group, but its sister group is unresolved. Morphologically, Odontoponera has several autapomorphies (denticulate clypeal margin, pronotal spines, and denticulate-emarginate petiolar scale) which readily distinguish it from other ponerines. Its deep striate sculpturing is also unique within the Odontomachus group (Paltothyreus has only shallow striate sculpturing), though Diacamma and Ectomomyrmex in the Ponera group have both convergently evolved deep striate sculpturing. In short, there are no morphological characters suggesting a close relationship with any other particular genus. Odontoponera is apparently yet another product of the early explosive radiation of the Odontomachus group.