Subgenus Anomma Shuckard (1840c: 326)

Diagnostic Features - Antennae with 11 segments and at least some joints of funiculus longer than width. Pygidium impressed with sharp margins.

Analysis of present knowledge, with a key to species and to a comparison of the gastral apices - Anomma keys

General summary

The well-known Driver Ants, living and moving in vast colonies - between 2,000,000 and 22,000,000 for Dorylus wilverthi (Raignier & van Boven, 1955). The subject of an extensive review by Hölldobler & Wilson (1990, Chapter 16, pages 588 ff). The treatise by Schneirla (1971) compared findings for the Neotropical Army ants, mostly genus Eciton, and the African Driver Ants but nearly all the information on the latter was derived from the work of Raignier & van Boven (1955). Gotwald (1974) added to the knowledge of the behaviour and predatory habits. The subgenus members apparently are restricted to tropical forests, or semi-cleared land in Africa. Bernard (1952) noted that the subgenus appeared to be rare in uplands, with only D. molestus (stanleyi) known from above 2500 m; he added that the Congo forests had yielded 12 species and that the Mt. Nimba collections from Guinea had provided one more species.

Particularly curious are the huge wingless dichthadiigyne queens and the bizarre "sausage fly" males.

The first description of an Anomma species was of a male specimen in 1802 (Dorylus nigricans Illiger) long before the Driver Ant workers (Anomma burmeisteri Shuckard, 1840c) and remaining unassociated with the Driver Ant workers for another decade (Anomma rubella, Savage, 1850). Uncertainty over that association of males with workers since has been cast into doubt by the work of Raignier & van Boven (see below), who reported that males of one species could be found accompanying, or at least very close to, trails of workers of a clearly distinct second species.

The queen was first described by E. André, in 1900, under the name Anomma nigricans [Sur la femelle probable de l'Anomma nigricans Ill. (Hym.) Bull. Mus. Nat. Hist. Paris, 6, 364-368] but Wheeler (1922) had this as the queen of Dorylus wilverthi, and it was not listed by Bolton (1995). Specimens photographed by Raignier & van Boven (1955), together with workers I have scanned, are shown left. Raignier & van Boven were the first to find all three life stages, of Dorylus wilverthi, in a single nest, possibly even today this is the sole finding of all forms together for a single species.

Here I offer a step towards revision of the status of the members of the subgenus Anomma, based on specimens sent to me and literature studies, especially the detailed review of historic literature and of specimens by Raignier & van Boven (1955). The main constraint on the latter was that they examined only specimens from the Congo Basin (old Belgian Congo); either collected by them around Yangambi, or held in the Royal Museum of the Congo in Tervuren, Belgium. It should be understood that my revision is not based on an examination of type specimens or other material held in the great museums. I hope, however, that it will meet my primary objective for the whole website, that is to enable a field worker or others without easy access to museum collections to identify the specimens before them

NOTE - it seems from Raignier & van Boven (1955) that only one species, Dorylus (Anomma) wilverthi, can be definitively stated as having all three life forms, male, female and workers, collected together from a nest (by them). They described how the finding of dealated males in migrating columns does not guarantee the males are associated with the workers in the column, instancing an occasion when they found a male of Dorylus (Typhlopone) in a wilverthi column. Thus, what from the literature appears to be perhaps the best known and most widespread member of the subgenus, Dorylus (Anomma) nigricans Illiger, actually is definitively known solely from the male. The vast majority of the references to "nigricans" most probably should be given under the definitive name of the worker described as Dorylus (Anomma) burmeisteri by Shuckard (1840c: 26).

Raignier & van Boven (1955) also emphasise the problem with evaluating the merits of the numerous descriptions of varieties made by the early taxonomists. Differences in colour were used to justify descriptions of new "varieties", such as pallidus and rubellus, but often the author had seen only one or very few specimens. Raignier & van Boven described how, in their studies of colonies in the field, it was not uncommon to see pale specimens, simply because the individual ants were not fully matured. To illustrate this, the illustration (right) shows several specimens taken by Professor S. Uehara from a migrating Driver Ant column at Mahale in Tanzania. As always - a picture is worth a thousand words!

Note on "Dorylus (Anomma) nigricans Illiger"

Bolton (1995: 179) gave a blanket list of the following under the main species name nigricans :-
nigricans s.s. type locality Sierra Leone (Dorylus nigricans, Illiger, 1802: 188, male; in subgenus by Emery, 1895j: 710, illustrated)
subspecies arcens, burmeisteri, molestus, pallidus, rubellus, sjoestedti, sjostedtiwilverthi, terrificus.

The species was named solely from a male specimen, with no associated worker or queen stages. Some light on the situation may be in the Haldeman (1849a) paper on Savage's collection of rubella "red drivers" from Gabon, with a column amongst which were three males; this is at . Haldeman, however, did write "if Dorylus nigricans is taken as the male of rubella"

Emery (1895j: 706) had a short key separating the workers using :-
Petiole longer than wide, with the posterior wider than the anterior. for what he gave as nigricans Illig. (burmeisteri Shuck.), separating TL max 10.5 mm - burmeisteri as the indicative sp, with varieties molestus Gerst. and rubellus Savage; and, TL max 13 mm for subspecies arcens Westwood.
Petiole wider than long, with rounded sides, TL 8 mm, gerstaeckeri Emery.

Wasmann (1904b) reviewed Dorylus (Anomma) nigricans Ill. subsp. burmeisteri Shuck. and what he regarded as the then known varieties. This is at . Santschi (1930a) provided what he called a description of the neuters of Dorylus (Anomma) nigricans. This is at . However, Santschi makes no reference to the collections (from Bamako, Mali, then French Sudan, by J. Andrieu) as including a queen, let alone the male, which Santschi noted as still unknown. He also provided a list of what he regarded as stirps and varieties of nigricans.