Dinoponera

Dinoponera is a strictly South American genus in the subfamily Ponerinae, tribe Ponerini, commonly called tocandiras or giant Amazonian ants (Zahl 1959, Fourcassié and Oliviera 2002, Haddad et al. 2005). These ants are generally less well known than Paraponera clavata, the bullet ant or hormiga bala (Haddad et al. 2005), yet Dinoponera workers may surpass 3cm in total body length, making them the largest in the world. The genus has been found from montane rainforest on the eastern slope of the Andes in Perú, Ecuador and Colombia to savannah and lowland rainforest in Brazil, Guyana, south through Bolivia, Paraguay and Argentina. (Lenhart, Dash & Mackay, 2013.) The genus is also notable for reproducing via gamergates (with the loss of the queen caste).

Identification
Lenhart, Dash & Mackay (2013) - Size (TBL > 2.5cm) can easily distinguish Dinoponera from other worker ants. Two laterally projecting clypeal teeth and rows of spines on the pygidium and hypopygidium will further distinguish this genus. The gamergates of Dinoponera are not distinct from workers in their external morphology (Haskins and Zahl 1971, Araujo et al. 1990, Paiva and Brandão 1995, Monnin and Peeters 1998). True gynes have not been found in this genus.

Schmidt and Shattuck (2014) - Dinoponera workers are unmistakable due to their enormous size. Other diagnostic characters (in combination) include: subtriangular mandibles, clypeal teeth, complex metapleural gland orifice, toothed tarsal claws, and stout hypopygial spines. Some of these characters are synapomorphic with Pachycondyla, which is sister to Dinoponera and the most similar genus morphologically. Pachycondyla lacks the huge size, subtriangular mandibles, clypeal teeth, and toothed tarsal claws of Dinoponera. Streblognathus bears some resemblance to Dinoponera, given its large size, subtriangular mandibles, clypeal teeth, and forward facing eyes, but Streblognathus has a novel fin-shaped petiole and lacks the complex metapleural gland orifice, toothed tarsal claws, and hypopygial spines of Dinoponera, and is somewhat smaller.


 * Key to New World Genera of Ponerinae

Distribution
Dinoponera is a strictly South American genus, found from montane rainforests on the eastern slope of the Andes in Perú, Ecuador and Colombia to savannah and lowland rainforest in Brazil, Guyana, south through Bolivia, Paraguay and Argentina (Lenhart et al., 2013). Lenhart et al. also provide maps showing the distribution of each Dinoponera species.

Species richness
Species richness by country based on regional taxon lists (countries with darker colours are more species-rich). View Data



Biology
Schmidt and Shattuck (2014) - Dinoponera is one of the best studied ponerine genera, due to its interesting social behaviors and large body size, which makes it relatively easy to work with. In particular, the papers by Monnin and colleagues document in unprecedented detail the social and reproductive behaviors of Dinoponera, especially of Dinoponera quadriceps (e.g., Monnin et al., 1998, 2002, 2003; Monnin & Peeters, 1997, 1998, 1999; Monnin & Ratnieks, 1999, 2001; Peeters et al., 1999; Hart & Monnin, 2006; also Hart & Ratnieks, 2005). We will only briefly summarize their results here, with the caveat that much of this information stems from studies of D. quadriceps alone, and its general applicability to the entire genus is in some cases uncertain.



Dinoponera colonies generally contain fewer than 100 workers, though colony size varies among species (Fowler, 1985; Paiva & Brandão, 1995; Fourcassié & Oliveira, 2002; Vasconcellos et al., 2004; Monnin & Peeters, 2008). Dinoponera has completely lost the queen caste and reproduction in each colony is instead performed by a single mated gamergate worker who is the top (alpha) individual in a ranked dominance hierarchy (Haskins & Zahl, 1971; Monnin et al., 2003). Below her in the hierarchy are three to five subordinate workers who vie with one another for the opportunity to succeed the alpha once she dies (Monnin et al., 2002; Peixoto et al., 2008). These hopeful reproductives perform little work in the colony and represent a drain on the colony’s resources (Monnin & Ratnieks, 1999, 2001; Monnin et al., 2003; Hart & Monnin, 2006). The remaining workers perform most of the work for the colony and also police the colony, punishing high-ranking workers who attempt to prematurely overthrow the alpha (Monnin & Ratnieks, 2001; Monnin et al., 2002). This policing is quite effective, as early replacement of the alpha is apparently rare (Hart & Monnin, 2006).

A newly annointed alpha worker briefly leaves the colony and mates with a single male (Monnin & Peeters, 1998). Subordinate workers do not mate, but sometimes lay haploid eggs which will develop into males if the alpha does not discover and cannibalize them (Dantas de Araujo et al., 1990; Monnin & Ratnieks, 2001). Alpha workers have a different cuticular hydrocarbon profile from other workers, and this profile is transferred to their eggs, allowing them to identify the eggs of subordinates (Monnin & Peeters, 1997; Peeters et al., 1999). The hydrocarbon profile is apparently related to ovarian activity, and allows workers to assess the rank and reproductive status of each member of the colony (Monnin et al., 1998; Monnin & Peeters, 1999; Peeters et al., 1999; Monnin & Ratnieks, 2001).

As with most ponerines lacking winged queens, colony reproduction in Dinoponera occurs via fission, with workers carrying brood and males to new nest sites and recruiting other workers via tandem running, with apparently no chemical trail (Dinoponera australis: Fowler, 1985; Dinoponera gigantea: Overal, 1980). Nests are built into the soil, can be quite extensive, and house diverse communities of myrmecophiles including inquiline Pheidole species (Zahl, 1957; Hermann et al., 1994; Paiva & Brandão, 1995; Vasconcellos et al., 2004). Workers are not generally aggressive but can deliver a painful sting if provoked (Allard, 1951; Zahl, 1957; Hermann et al., 1994). Dinoponera workers forage diurnally or crepuscularly on the ground, and are generalist predators of insects and opportunistic scavengers of fruits and other food sources (Oldham et al., 1994; Hermann et al., 1994; Paiva & Brandão, 1995; Fourcassié & Oliveira, 2002; Monnin et al., 2003; Araújo & Rodrigues, 2006). Workers always forage individually (Zahl, 1957; Haskins & Zahl, 1971; Fowler, 1985; Fourcassié & Oliveira, 2002; Araújo & Rodrigues, 2006). Orientation and navigation by foraging D. gigantea workers were studied by Fourcassié et al. (1999).

The large size and interesting behaviors of Dinoponera have made them attractive model systems for histological and biochemical research, including studies of the mandibular gland (Oldham & Morgan, 1993; Oldham et al., 1994; Hermann et al., 1994), Dufour’s gland (Hermann et al., 1994, Morgan et al., 2003), sting apparatus and venom gland (Hermann et al., 1994; Morgan et al., 2003), convoluted gland (inside venom reservoir; Schoeters & Billen, 1995), post-pharyngeal gland (Schoeters & Billen, 1997), and antennal sensillae and glands (Marques-Silva et al., 2006). Interestingly, Dinoponera lucida has the highest number of chromosomes known for any hymenopteran (2n=120), though the total number ranges from 2n=106 to 2n=120 and the significance or cause of this large number and variation is unknown (Mariano et al., 2004; Barros et al., 2009).

Nomenclature

 *  DINOPONERA [Ponerinae: Ponerini]
 * Dinoponera Roger, 1861a: 37. Type-species: Ponera grandis (junior synonym of Ponera gigantea), by monotypy.

Description
Schmidt and Shattuck (2014):

Worker
Huge (TL 25–40 mm; Kempf, 1971; Paiva & Brandão, 1995) ants with the standard characters of Ponerini. Mandibles subtriangular, with roughly five teeth and without a distinct basal angle or basal groove. Anterior margin of clypeus with a pair of long anteriorly-directed teeth. Frontal lobes moderately large. Eyes moderately large, located anterior of head midline and relatively forward-facing. Posterolateral corners of head prominent. Metanotal groove reduced to a subtle suture. Propodeum broad dorsally. Propodeal spiracles slit-like. Metapleural gland orifice with a posterior U-shaped cuticular lip and a lateral groove. Tarsal claws with a single tooth. Metatibial spur formula (1s, 1p). Petiole nodiform, with a blunt dorsal longitudinal ridge. Gaster with a strong girdling constriction between pre- and postsclerites of A4. Stridulitrum present on pretergite of A4. Hypopygium with a row of stout spines on either side of the sting. Head and body smooth to sparsely punctate, with sparse to abundant pilosity and patchy pubescence. Color black. See also description in Lenhart et al. (2013).

Queen
Absent, reproduction instead being performed by gamergates.

Male
See description in Lenhart et al. (2013).

Larva
Described for D. gigantea by Wheeler & Wheeler (1986a).