The Ants of Africa
Chapter 2 - Geography - West Africa & the Congo Basin - introduction

Countries included as in "West Africa" and the Congo Basin

Ragge (1980) expressed his preference for the term 'Afrotropical Region', rather than the long-held and, in my view, now misunderstood term 'Ethiopian Region', thus, supporting the view of Crosskey & White (1977) - a concept with which I fully agree.

"West Africa" - any selection would have an arbitrary basis and I have chosen to concentrate on the northern limit of the 500 mm isohyet and from the western limit of land across to the eastern border of Cameroun. In west to east order, the countries thus included are Senegal, Gambia, Guinea Bissau, Guinea, Sierra Leone, Mali (southern), Liberia, Ivory Coast, Ghana, Upper Volta, Togo, Benin, Nigeria and Cameroun; the names are denoted in bold in the species catalogue. A similar choice was that made by the editors of the West African Nature Handbooks, published by Longman, London, in the early 1970s. Map 1 shows the approximate extent of the various vegetation areas within West Africa.

The summary sections in the linked sub-Chapters give the main geographic areas of West Africa from which ant studies have been reported since 1950. A useful source of the earlier reports is Entwistle (1972) who was able to draw on many internal documents and other items which appear never to have been published in a recognised scientific journal. His chapter on ants has no references to work from West Africa earlier than that of Strickland (1951a, b), although he draws attention to the work of Wheeler (1922) in the (then) Belgian Congo, for a separation of the subgenera of Crematogaster. I have listed information primarily for "West Africa", as defined below. There are, of course, species with wider distributions, some from throughout tropical Africa, and many known also from neighbouring eastwards areas, such as in Gabon, Congo and Zaïre (including the findings of the famous Belgian Congo expedition reported by Wheeler, 1922).

The climatic zones covered are the tropical forest zone and the Guinea savannah (see also Lévieux, 1983). The rainfall in these zones is approximately 3000-1500 mm (from the coast northwards) and 1500-500 mm (again decreasing northwards) respectively. An interesting ecological feature is the so-called Dahomey Gap, where the Guinea savannah extends southwards to the coast between eastern Ghana, through Togo and Benin, to the western border of Nigeria. Ragge (1980, 79-82) described how this gap appears to affect the distribution of Phaneropterine grasshoppers. Of the nine genera endemic to West Africa, two genera are found only west of the gap and five genera only to the east. He attributed the disjunct distribution to their being forest species, adding that the gap probably is of long standing, although possibly bridged during Pleistocene pluvial periods. Similarly, the montane area of western Cameroun means there is no more than a narrow belt of tropical forest between the area bordering Nigeria and the main rain-forest area of Cameroun. The latter area, therefore, may have more in common with the vast Congo Basin rain-forests than with "West Africa", and Bolton (1981b) wrote of a Cameroun ant (Cyphoidris exalta) as being from "Central Africa". Indeed Ragge (1980, 80) wrote of the "genera endemic to West Africa (including parts of Uganda, Zaïre and Angola)".

"The Congo Basin" - in late-2001, I decided to add the countries of the Congo Basin. My prime reason was that the material sent to me from Cameroun included species previously not known to me from my search of the literature. The expansion is only as a collective group and I have not separated the modern countries.

The map below shows the extent of the expanded area - "West Africa & the Congo Basin". It is worth noting that recent ant surveys in eastern and southern Africa (e.g. French & Major, 2001; Robertson, 2002; Tshiguvho et al., 1999) show quite different assemblages of ant species to those of West Africa and the Congo Basin.

{Ecological regions of West Africa & the Congo Basin}

A brief note on what could be called "Imperial Geography" may prove useful to those studying the early collection records, even as late as Wheeler (1922). From the eastern border of modern Sierra Leone eastwards to the line of the Equator was frequently called the Coast of Guinea. This again was subdivided into the (westernmost) Grain Coast, the Ivory Coast, the Gold Coast and the (easternmost) Slave Coast (from the Volta River east to the Lagos River). French West Africa included the modern states of Senegal (sometimes referred to as Senegambia, including parts of modern Mali), Guinea (French Guinea), Mali (French Sudan), Ivory Coast, Togo, Benin (Dahomey), Upper Volta (also in French Sudan), and Niger (Niger Colony). French Equatorial Africa encompassed Chad, Cameroun (or rather the eastern part, Cameroons), the Central African Republic, Gabon and Congo. Guinea Bissau was formerly Portugese Guinea. The former British Empire included Gambia, Sierra Leone, Ghana (Gold Coast), Nigeria and western Cameroun (pre-1918 the western part was German West-Africa and then became incorporated in Nigeria). Liberia has long been known by that name.The Spanish Territory of Rio Muni corresponds to the modern Equatorial Guinea.

In reviewing the original descriptions now (late-2003) made available by the efforts of Donat Agosti, I realised that the geography as understood in the late-19th century was not fully comprehended by modern researchers. For instance, in his great Catalogue, Bolton (1995) has a few instances of type location given as "SUDAN" - this modern students would take as being the large Republic of Sudan, in north-east Africa. Most notably these relate to findings in Santschi (1930a) from collections by Andrieu, near Koulouba (13°29'N 9°08'W, a 100 km or so north-west of Bamako), that is in modern Mali. In the nineteenth century, however, the term "Sudan" also applied to the huge area of French dominated north Africa, stretching from the Atlantic right across to the British-dominated territory, now the modern Sudan.

In my possesssion I have a copy of the Eton Compendium of Geography, edition published around January 1856, by C.G.N. of King's College, London; the first edition, by Rev. Aaron Arrowsmith, having been published in 1831. I have reproduced the relevant pages as pdfs which can be read by using the links: Soudan or Nigritia {original description}; Lower Guinea (Angola and Congo Basin south of the Equator) {original description}; Upper Guinea (Western Africa {original description}.

Distribution and collection areas

In the chapters and sections which deal with individual species, the notes on distribution and bionomics are derived from as many sources as possible but these remain relatively few both in numbers and in their geographical distribution. My original guide concentrated on the forest zone of Nigeria simply because that was where I worked and from where nearly all the illustrated species originated. In a number of instances the Genus was listed only because its members were known from adjoining ecological areas of Nigeria, or were likely to be discovered in Nigeria, being known elsewhere in West Africa. All told, the collections I examined and drew from CRIN and other parts of the forest zone, mainly cocoa farms, included representatives of 46 genera and over 200 species or morphologically separable forms. The list of world genera in Hölldobler & Wilson (1990) gives some 93 genera from Africa (the Ethiopian zoogeographical Region) but a good number of these are from other ecosystems, such as open savannah and desert, and others are known from perhaps only a single collection elsewhere on the continent. Bolton (cited in Hölldobler & Wilson, 1990) has made a rough estimate of there being around 2,500 ant species described from Africa. By extrapolation from the paper by Belshaw & Bolton (1994b), who surveyed leaf litter and added perhaps 74 species to the known list from that single habitat stratum, one can reach a figure of around 350 likely species of ant from the Ghanaian forest zone (more details).

2 - Ghana 2 - Nigeria 2 - Cameroun 2 - Ivory Coast 2 - Guinea 2 - Other West African Countries 2 - Congo Basin
©1998-99, 2002, 2003, 2004, 2006, 2009, 2012 - Brian Taylor CBiol FSB FRES
11, Grazingfield, Wilford, Nottingham, NG11 7FN, U.K.