Dorylus

The Afrotropical ‘driver ants’ of this genus epitomize the army ant lifestyle, but they represent only a fraction of the diversity of Dorylus. Most species are much less commonly observed, and forage underground or in leaf litter.

Hita Garcia, Wiesel and Fischer (2013) - The army ant genus Dorylus is mostly known for the spectacular swarm raids performed by some epigaeic species, mostly belonging to the subgenus Anomma, better known as "driver ants". These species perform huge swarm raids along the ground and lower vegetation with hundreds of thousands of blind, polymorphic workers to hunt down a great variety of prey taxa in large quantities, predominantly invertebrates (Gotwald, 1982, 1995). However, many more species within the genus live and hunt hypogaeicly and these army ants are generally less visible than their epigaeic relatives (Berghoff et al., 2002). Hypogaeic species hunt in columns and many species are known to be specialised predators of other social insects, such as termites or other ants (Darlington, 1985; Gotwald, 1982, 1995; Schöning & Moffett, 2007). Almost all species of Dorylus, like other army ant genera, live in monogynous colonies with dichthadiiform queens that have a massive egg-laying capacity, e.g. three to four million eggs per month in “driver ant” queens (Raignier & van Boven, 1955). In addition, Dorylus colonies migrate in irregular intervals to new nesting sites and new colonies emerge through colony fission (Gotwald, 1982, 1995).

Identification
Garcia, Wiesel and Fischer (2013) - The taxonomic condition of Dorylus, especially for the African continent, can be classified as chaotic and useless for identification purposes. On a global basis, 59 species and 68 subspecies are recognised (Bolton, 2012), although the taxonomic validity of many of these taxa is highly questionable. The problem is that most descriptions were based on a single caste, and careful examination of taxa in order to find evidence for conspecificity among these is very rare (Schöning et al., 2008). Also, no modern taxonomic revision is available, which dramatically increases the difficulties to identify Dorylus to species level. Nevertheless, identification to subgenus level can be well performed with the keys provided in Gotwald (1982).

Distribution
This genus is distributed throughout the Old World tropics and subtropics, but the majority of species are found in the Afrotropical zoogeographical region (Gotwald, 1982, 1995).

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



Biology
Because some species of this lineage are so conspicuous and are the most important arthropod predators of the Afrotropics, this group has attracted considerable attention. The best studied species include the Afrotropical species that forage above ground (Raignier and Boven 1955, Raignier 1972, Gotwald 1995), but one subterranean species, D. laevigatus has been the subject of some work (Berghoff et al. 2002a,b, 2003a,b, Weissflog et al. 2000). Good overviews of Dorylus biology can be found in Raignier and Boven (1955) and Gotwald (1995). The surface- and leaf litter-foraging species have been collectively referred to as ‘driver ants’ (Savage 1847), and traditionally classified in the polyphyletic subgenus Anomma (see Taxonomy and phylogeny above). Here I follow this convention and use the terms ‘driver ants’ and ‘surface-‘ or ’epigaeically- foraging species’ interchangeably. The life cycle of Dorylus colony is similar to that of Eciton and many other army ants but there are no pronounced nomadic and statary phases. The brood production is not synchronized (Gotwald 1995, Schöning et al. 2005b), and the colonies move from old to new nesting sites at irregular intervals (Gotwald and Cunningham van Sommeren 1990, Schöning et al. 2005b). A mature colony will produce about a dozen virgin queens and eventually undergo fission. About half of the worker force will depart with the old, fertilized queen, while the other half will remain with the virgin queens. Ultimately, all except one of the new queens are cannibalized (Raignier 1972). The new colony does not produce sexual brood until the workers mothered by the old queen have died (Kronauer et al. 2004). Copulation in Dorylus has been observed only once (Kronauer and Boomsma 2007a). Males collected at lights and two inseminated queens from established D. molestus bivouacs were coupled under laboratory conditions. The male first uses his sickle-shaped mandibles to grasp the queen behind her petiole and performs bending movements, searching the tip of the queen’s abdomen. Once engaged, the pairs remained in copulation for five to ten hours. After this period, the male relaxes his grip on queen’s petiole but remains connected to the queen. Twenty hours after the copulations, the two pairs were killed and dissected, both males remaining attached to the queens. The males apparently succeeded in transferring sperm to the queens, and the dissections confirmed that the male accessory testes were empty after the copulations. Despite these observations, Kronauer and Boomsma (2007a) find little evidence for army ant queens re-mating later in life and point out that the males were not attracted to old queens in most trials.

Nomenclature

 *  DORYLUS [Dorylinae]
 * Dorylus Fabricius, 1793: 365. Type-species: Vespa helvola, by monotypy.