# Dorylus
**Dorylus** is a genus of army ants in the subfamily Dorylinae of the ant family [Formicidae](https://www.edgepedia.org/formicidae), established by Fabricius in 1793 and known for the African "driver ants" whose swarm raids can sweep more than 1,000 m2 of ground in a single day.[1](https://www.itis.gov/servlet/SingleRpt/SingleRpt?print_version=PRT&search_topic=TSN&search_value=573941&source=to_print) • [2](https://pmc.ncbi.nlm.nih.gov/articles/PMC1852301/) The genus holds some of the largest single-queen insect societies known, with colonies of *Dorylus wilverthi* estimated at between 2,000,000 and 22,000,000 ants.[3](https://www.antsofafrica.org/ant_species_2012/dorylinae/anomma.htm)
| Key fact | Detail |
|---|---|
| Classification | Genus *Dorylus* Fabricius, 1793, family Formicidae, subfamily Dorylinae; current standing valid[1](https://www.itis.gov/servlet/SingleRpt/SingleRpt?print_version=PRT&search_topic=TSN&search_value=573941&source=to_print) |
| Colony size | *D. wilverthi* colonies between 2,000,000 and 22,000,000 ants; single-queen *Dorylus* colonies can reach 20 million workers[3](https://www.antsofafrica.org/ant_species_2012/dorylinae/anomma.htm) • [4](https://pmc.ncbi.nlm.nih.gov/articles/PMC1088800/) |
| Raiding | Surface-raiding species form massive swarm raids on the ground and in low vegetation, sweeping areas of 1,000 m2 or more per day[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC2842746/) • [2](https://pmc.ncbi.nlm.nih.gov/articles/PMC1852301/) |
| Reproduction | Queens are permanently wingless; new colonies arise by fission, and gene flow is mediated mainly by winged males that enter foreign nests to mate[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC2842746/) |
| Life cycle | Similar to *Eciton* and other army ants, but without pronounced nomadic and statary phases[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC4982377/) |
| Evolution | Crown-group origins of the four major army ant lineages, including *Dorylus*, fall between 37 and 6 million years ago[7](https://pmc.ncbi.nlm.nih.gov/articles/PMC4021219/) |
| Sexual dimorphism | Males ("sausageflies") and females ("driver ants") are so different that a third of species are known only from males, a fifth only from workers, and a tenth only from queens[8](https://onlinelibrary.wiley.com/doi/10.1002/jmor.21410) |
## Army ant lifestyle
Army ants are defined functionally rather than by shared ancestry: the syndrome combines obligate collective foraging, frequent colony relocation (nomadism), reproduction by colony fission, and permanently wingless, highly specialized queens.[9](https://pmc.ncbi.nlm.nih.gov/articles/PMC8179172/) • [2](https://pmc.ncbi.nlm.nih.gov/articles/PMC1852301/) In a mass raid, tens of thousands of ants stream out of the nest in a column, or in the largest colonies a swarm, with a few scouts searching slightly ahead and laying pheromone trails back to the raid front when they find prey.[9](https://pmc.ncbi.nlm.nih.gov/articles/PMC8179172/) *Dorylus* species are generalist predators, mainly of invertebrates, whereas phasic species of *Aenictus*, *Eciton*, and other New World army ants rely heavily on brood of other social insects.[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC2842746/) • [6](https://pmc.ncbi.nlm.nih.gov/articles/PMC4982377/)
The colony cycle of *Dorylus* resembles that of *Eciton* but lacks pronounced nomadic and statary phases. In reproductive colonies of the montane forest species *Dorylus molestus*, the stay in a nest is highly variable, with a median of 17 days and a range of 3 to 111 days, so a brood-cycle pattern generator can be ruled out as the underlying driver.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC4982377/) • [10](https://refubium.fu-berlin.de/bitstream/handle/fub188/12374/06_chapter3.pdf?isAllowed=y&sequence=7)
## Colony size and gigantism
*Dorylus* colonies are among the largest single-queen insect societies, reaching 20 million workers, and a size-structured evolutionary model proposes that this gigantism arises from an arms race. The model predicts large colony size, battles between colonies, and highly asymmetrical colony divisions in *Dorylus*, while predicting smaller, non-combative *Eciton* colonies with equitable binary fission; these predictions agree with field observations.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC1088800/)
**Comparisons with Eciton.** Colonies of *D. wilverthi* in the [Old World](https://www.edgepedia.org/old-world) and *Eciton burchelli* in the New World retrieve prey items of almost identical size and have similar overall worker size ranges, yet 98% of *D. wilverthi* workers fall within the size range of the smallest 25% of *E. burchelli* workers. *Dorylus* compensates with teamwork: 39% of prey items and 64% of prey biomass are retrieved by teams, against 5% and 13% in *Eciton*. Working alone or in teams, *Dorylus* carry more per unit of ant weight, but *Eciton* are swifter; the ergonomic differences counterbalance, so colony-level performance is remarkably similar between the Old and New World species.[11](https://pmc.ncbi.nlm.nih.gov/articles/PMC1690180/)
## Taxonomy and phylogeny
The genus was long divided into subgenera, including the surface- and leaf-litter-foraging *Anomma*, the driver ants, and the nominotypical *Dorylus*. A molecular phylogeny showed that neither *Anomma* nor *Dorylus* sensu stricto is monophyletic: the subterranean species form two clades, and one lineage of *Dorylus* s.s. secondarily re-evolved subterranean foraging with morphological adaptations remarkably convergent on the ancestral underground state.[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC1852301/) A 2016 generic revision of Dorylinae consequently treated the traditional subgenera as species groups and consolidated the classification of the subfamily.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC4982377/)
The army ant syndrome itself evolved convergently in the Old and New World lineages. A 2019 phylogenomic study using 2,166 loci and sampling all 27 doryline genera and about 22% of doryline species found strong support for convergent evolution of the syndrome in the Old and New World, and described it as a case of long-term evolutionary stasis.[12](https://academic.oup.com/sysbio/article-abstract/68/4/642/5272507) [Divergence](https://www.edgepedia.org/divergence) dating places the crown-group origins of the four major army ant lineages, *Aenictus*, *Dorylus*, *Aenictogiton*, and the New World army ants, between 37 and 6 million years ago.[7](https://pmc.ncbi.nlm.nih.gov/articles/PMC4021219/)
## Sexual dimorphism and castes
*Dorylus helvolus* (Linnaeus, 1764) was one of the original 17 ant species recognized by Linnaeus, who knew the males as massive, hirsute wasps he placed in the genus *Vespa*. The winged males were so distinct that a separate family was designated for them, and the identity of the female remained confused for nearly a century until Savage fortuitously discovered males among raiding workers in 1849. The males are now called "sausageflies" and the females "driver ants."[8](https://onlinelibrary.wiley.com/doi/10.1002/jmor.21410)
The polymorphism is so extreme that a third of all species are known only from males, a fifth only from the aggressive workers, and a tenth only from the gigantic, blind, wingless queens. An anatomical study of *D. helvolus* found an inversion of the usual male-queen pattern: male *Dorylus* mandibles are extremely large while queen mandibles are poorly developed, and the authors proposed that the reproductive-limited mandible phenotype is canalized in *Dorylus*, partially decoupling the queen and worker castes.[8](https://onlinelibrary.wiley.com/doi/10.1002/jmor.21410)
## Colony fusion after queen loss
Queenless army ant colonies present a puzzle for theories of altruism, since workers would seem to gain nothing by joining unrelated colonies. Experiments on *Dorylus molestus* on the eastern slopes of Mt Kenya, where the species is abundant in forests up to 3,000 m altitude, showed that orphaned colonies frequently merge with neighboring queenright colonies, often within days of queen removal. Merging colonies usually lack direct co-ancestry but are probably distantly related through population viscosity. Male production by orphaned workers appears so inefficient that workers may maximize residual inclusive fitness by merging indiscriminately; worker chemical profiles rapidly change into a mixed colony Gestalt odor after fusion, consistent with acceptance of non-aggressive alien workers.[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC2842746/)
## Ecology
*Dorylus* ants prey heavily on other social insects, including termites. In Kenyan fungus-growing termite colonies of *Macrotermes michaelseni*, the ant species with lethal effects changes with colony development: opportunistic predators and recruitment-tracking ants attack early and middle stages, while subterranean group-foraging doryline ants such as *Dorylus juvenculus* dominate against late-stage colonies.[13](https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/dorylus) Because queens disperse on foot throughout their lives and new colonies arise by fission, gene flow within *Dorylus* populations is mediated mainly by the winged males that leave their natal colony to mate with young queens inside foreign nests.[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC2842746/)
## References
1. [ITIS Report: Dorylus Fabricius, 1793](https://www.itis.gov/servlet/SingleRpt/SingleRpt?print_version=PRT&search_topic=TSN&search_value=573941&source=to_print)
2. [A molecular phylogeny of Dorylus army ants provides evidence for multiple evolutionary transitions in foraging niche, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC1852301/)
3. [The Ants of Africa: Driver Ants (Anomma)](https://www.antsofafrica.org/ant_species_2012/dorylinae/anomma.htm)
4. [Arms races and the evolution of big fierce societies, Proceedings of the Royal Society B, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC1088800/)
5. [Colony fusion and worker reproduction after queen loss in army ants, Proceedings of the Royal Society B, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC2842746/)
6. [Generic revision of the ant subfamily Dorylinae (Hymenoptera, Formicidae), ZooKeys, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC4982377/)
7. [The rise of army ants and their relatives: diversification of specialized predatory doryline ants, BMC Evolutionary Biology, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC4021219/)
8. [Anatomy and evolution of the head of Dorylus helvolus, Journal of Morphology](https://onlinelibrary.wiley.com/doi/10.1002/jmor.21410)
9. [Colony expansions underlie the evolution of army ant mass raiding, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC8179172/)
10. [Migration behaviour of the army ant Dorylus molestus, chapter 3, Refubium](https://refubium.fu-berlin.de/bitstream/handle/fub188/12374/06_chapter3.pdf?isAllowed=y&sequence=7)
11. [Convergent evolution, superefficient teams and tempo in Old and New World army ants, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC1690180/)
12. [Convergent Evolution of the Army Ant Syndrome and Congruence in Big-Data Phylogenetics, Systematic Biology](https://academic.oup.com/sysbio/article-abstract/68/4/642/5272507)
13. [Dorylus, ScienceDirect Topics overview](https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/dorylus)
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*Topic: Encyclopedia › Life and health › Animals › Invertebrates › Arthropods › Insects › Bees, wasps, and ants › Aculeata: bees, wasps, and ants › Ants (Formicidae)*
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