The Ants of Africa CHAPTER 6 - Taxonomy Introduction

The Ants

CLASS INSECTA, PHYLUM ARTHROPODA, ORDER HYMENOPTERA, SUBORDER APOCRITA, SUPERFAMILY VESPOIDEA, FAMILY FORMICIDAE.

Format of the Taxonomic Section

In a single great work, Bolton (1995) has attempted, in his words, "to catalogue all the ants of the world". In its elder companion volume (Bolton, 1994), he provided a comprehensive listing of all taxonomic levels from genus upwards, with keys to all those levels. It is his grouping, order and nomenclature which is used here.

Notes on the most significant changes are given in the appropriate sections of the text. The presently accepted nomenclature is indicated by the use of bold type, with outdated names following where appropriate. At the species level the nomenclature also follows the appropriate publications, with identifications in my previous Field Guide corrected on Bolton's advice, in personal communications in 1976 and 1980. Sadly, belying the quotation from Bolton (1995), several major genera have still to be revised, a matter of some concern as they are genera containing many species of importance to applied workers. An added complication, of course, is that no list is at all likely to be final. For instance, Belshaw & Bolton (1994b) list three unidentifiable species of Monomorium from leaf litter in Ghana and those species fall into a genus which was comprehensively revised by Bolton as recently as 1987.

The present text, however, remains essentially a Field Guide and, thus, the primary identification of species is intended to be by a combination of the illustrations and the notes, particularly the various dimensions. Nevertheless, wherever possible keys derived from those in modern taxonomic papers are given. When using taxonomic keys and reading descriptions of genera, or other large groupings, it is all too common to encounter the word "usually". This is an unfortunate fact of a taxonomist's life and cannot be avoided simply because of biological variation. Thus, for sound diagnosis it is necessary always to look for a combination of morphological characters and never to rely on first impressions of a single major character. Sometimes, this results in what appears to be strange inconsistency, even by a single author, in separating species, or even genera. Small morphological characters may be definitive, as, for example, within the Myrmicinae, where a dichotomous key (Bolton, in Hölldobler & Wilson, 1990) splits at 10-segmented antennae for Decamorium, and yet one then finds the apparently contrary acceptance of 11- or 12-segmented antennae for Tetramorium. The only answer is that the museum taxonomists routinely strive to access a wide range of specimens (both from within a 'species' and between 'species') and visit other museums, borrow material and so-on. Thus their arbitrary decisions, for that is what they are, are made in good faith from the widest possible perspective. It must be admitted, however, that some decisions are puzzling for example, the separation of Leptothorax angulatus and Leptothorax grisoni, which differ solely in colour and intensity of otherwise similar sculpturation (Bolton, 1982), but not of the similarly distinct variants of Tetramorium quadridentatum (Bolton, 1980).

Along these lines, my recent (mid-1999) receipt of a copy of Bernard (1952) has underlined my (minor) misgivings regarding the extensive revisonary work by Barry Bolton. None of the English language texts had given me any indication of the quantity, let alone quality, of work done by Bernard in identifying ants collected during the the major ecological surveys of the Mt. Nimba massif in Guinea, in 1942 and 1946. Although, by and large, specimens described as new species by Bernard were examined by Bolton, the latter rarely mentions other Mt. Nimba records, often not even including Guinea in the distribution list in his keys. Further, there are instances where Bolton is disparaging of Bernard's taxonomic conclusions but careful reading of the French text suggests that this may be unfair. It also highlights how Bolton appears very happy to act as a "lumper" by synonymizing earlier definitions of species, subspecies and varieties but then, quite probably correctly, to act as a "splitter" in differentiating many new species on the basis of single specimens.

Finally, in the keys I have not indicated the countries from which each species is known. This is because the keys relate only to ants known from "West Africa & the Congo Basin" (see Chapter 2) and because distribution tends to reflect the activity of collectors rather than the geography of the insects. Such information as is available is, however, given in the individual species notes. Note - from 2007, I now give the known countries in all the keys and those have expanded to cover all of sub-Saharna Africa, and, in some cases, e.g. Lepisiota, North African and Middle Eastern species.

In all instances, definitive species names are given with the name of the original author. I have endeavoured to sight and list in the References all modern (post-1940) taxonomic papers covering West African ants and, in a separate section have listed many early references, providing the names of "new species". All the early references can be found in Bolton (1995). In general, I took Bolton (1973a) as my starting point for the taxonomic literature, but those interested in bibliographies of the pioneers in ant taxonomy will find that Ettershank (1966) is another useful source. For an in-depth search for taxonomic information a good source is Zoological Record.

Now (2003) I have included a link to the web-based Hymenoptera Name Server from almost all of the definitive species (essentially those listed in Bolton, 1995). Note that some of my own suggested revisions may not be incorporated on the server. An example of the link appears right and clicking the image will take you to the appropriate page of the server (as an example, the link here leads to the species Tetramorium aculeatum).

Among the most recent papers are several dealing with "higher classification". A modicum of information from those rather specialist works is dealt with in the chapter section "Higher Levels of Classification and Phylogeny" but one aspect needs to be mentioned here. Bolton (1990c) drew attention to a problem which causes confusion in enumerating the species within each taxonomic group, such as a subfamily or genus. That is the number of species which are known only from a single form, such as the worker or queen. He particularly highlighted the many species of Dorylines which are known only from the large males, which are nocturnal and readily attracted into light-traps. In the Afrotropical zone, the genus Dorylus had valid names for 54 species of which 23 were known only from males. Similarly, the genus Aenictus had 33 species names of which 19 were known only from males. Accordingly, I have sought to indicate the form or forms which have been described in the notes on each named species.

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