Dirickx, H. G. 1998. Catalogue synonymique et géographique des Syrphidae (Diptera) de la région Afrotropicale. Museum d’histoire naturelle Geneve. 187pp.
[Vicky Morgan, 2001-06-01]
Thanks to their relatively large size, their often coloured and shiny body and their abundance in numerous natural habitats, the Syrphidae have held the attention of entomologists for sometime. Even as early as the pre-linnean period some species were well known. In the 10th edition of Systema Naturae, many syrphids were described, however none of which belonged to the Afrotropics. Syrphidae form part of the Diptera Brachycera - Aschiza group and thus are part of a group which has the reputation for being relatively well known from a systematic and faunistic point of view. The family is clearly differentiated by a series of morphological characteristics drawn along the veins. The most remarkable of these characteristics is the presence of a longitudinal trace vein often weakly sclerotised, situated between the radial and medial section of the wing. This vein is known as the vena spuria and cuts across the radio-median vein. Moreover, the radial posterior and discal cells are closed. In nature, the onlooker distinguishes syrphids by their swift flight, and their ability to hover in the air and change direction sharply. Adults of the majority of species are flower-coloured and the inflorescence of the family Compositae in particular are visited assiduously, the adults feed on pollen and nectar. Other species prefer to visit the petals where they collect pollen and honey from aphids. Contrasting with the uniformity of the alimentary regime of adults, a very large trophic diversity characterises the life cycle of larvae. It is possible to distinguish four main groups according to feeding habits and the environment in which the larvae develop. The zoophagous species hunt down aphids, psyllidae and caterpillars on which they feed. The second group comprises of phytophagous larvae that attack the tissues of several plant organs including fungus, like leaves, stalks, bulbs and tubers. The decomposing matter gathers together the saprophagous larvae living in the pools of dirty water or in the water retained within tree cavities, where they filter through the organic decomposing sediment. Some species are coprophagous (genus Rhingia) while others develop in the liquid oozing from the wounded trees. Lastly, a certain number of syrphids develop in the nests of social insects (bees, wasps and ants), the most common being the species of the genus Microdon whose larvae resemble a small mollusc.
The Syrphidae at the present day comprise more than 5000 species spread across all the continents. The knowledge of regional fauna is however very uneven. The palaearctic species, comprising about 1600, are the best known. For thirty years or so, numerous groups have been given detailed revisions, relying on external morphology as much as the comparative study of genitalia. Considerable progress has thus been made in terms of the definition of individual taxa and their phylogenetic relations. Extensive field research, making frequent call on the new methods of trapping have furthermore made it possible to clarify and draw up detailed charts of distribution. These conditions are not always associated in all the zoogeographic regions. Thus, almost all of the publications devoted to the fauna of syrphids from the African tropics consist of descriptions of new species and faunistic lists. The only synthesis paper structured on the whole continent is the regional monograph entitled “The Syrphidae of the Ethiopian Region” by Bezzi (1915). This paper was based on an important collection built up by the Imperial Bureau of Entomology and held at the Natural History Museum, London. The author gave identification keys for all the genus and all the species represented in the collection as well as a description of sixty new taxa for the region in the paper. The total inventory of syrphids known from Africa rose at this time to 249 species. From that time, numerous contributions have come to light but they almost all boil down to rendering accounts of exploration voyages or to descriptions of taxa hitherto unpublished. Papers on taxonomy and revisions particularly remained scarce. One must however mention the important publications of Stuckenberg (1954), Thompson (1974), Hippa (1985, 1990) and Whittington (1992) who have clarified the systematics of the genera Paragus, Spheginobaccha, Hovaxylota, Vadonimyia and Graptomyza. In 1980 the Catalogue of the Diptera of the Afrotropical Region (Smith & Vockeroth, 1980) was published which put at Entomologists disposition the first comprehensive survey of Diptera from the African continent since the work of Kertész (1910). The Catalogue comprised 522 valid taxa of Syrphidae. The authors had established many new synonymies and enlarged the known distribution of several species.
The first two taxa of the region were described by Fabricius in 1781, followed by a third species originating from Guinea in 1805. The arrival of the 19th century brought the beginnings of Diptera exploration on the African continent. In 1818 and 1824, Wiedemann made known six species collected in South Africa around the Cape of Good Hope. A few years later, the same author described another series of taxa from various localities in Africa, followed from 1842 by the publication of “Dipteres Exotiques” by Macquart where 19 African Syrphidae were newly described for Science. In 1860, Loew published the first comprehensive paper on the dipterological fauna from South Africa in which he listed 50 African species. During the second half of the 19th Century, a group of about ten entomologists contributed once more to making public new syrphids from different localities on the African continent, reported by naturalists through their voyages.
With the coming of the 20th Century came a new period of exploration with the organisation of expeditions principally in central and southern Africa. The results of these grand voyages were published notably by Bezzi, Speiser, Hervé-Bazin, Curran, Hull and Keiser. The, often partial, study of collections accumulated by various large museums gave way to the description of numerous new taxa.
It is perhaps worth noting that in the recent past each new prospecting effort in a section of the Afrotropical Region has brought to light a not insignificant number of hitherto unpublished taxa. To give an example, one could cite the collections of the Lund University Expedition in South Africa, which allowed Hull (1964) to describe 27 new species of which 16 were under the one genus Eumerus. A few years later the fauna of syrphids from Madagascar were enriched by 57 new taxa at the publication of results of a year’s exploration carried out on the island (Keiser, 1971). It is highly likely that the new explorations, especially in the regions scarcely or not visited in the past, would enable an additional significant increase to the survey of Syrphidae from the African continent. The collections of the Musée Royal de l’Afrique Centrale (M.R.A.C.) at Tervuren, of l’Institut Royal des Sciences Naturelles de Belgique (I.R.Sc.N.B.) and of the Muséum National d’Histoire Naturelle de Paris (M.N.H.N.) which we have had the occasion to visit house moreover a good number of taxa not yet described. In conjunction with the effort to identify these new species, some studies should be dedicated towards taxonomic and geographic revisions of nominal genera or groups of species. For the majority of genera, more or less important, the literature available does not allow one to progress towards reliable identifications: the original descriptions are often incomplete and the existing identification keys are often ancient and only comprise a limited number of known taxa, or are totally lacking. In these conditions, the setting up of a preliminary taxonomic clarification is essential. We hope that this paper will serve as a basis for this type of study.
As with the vast majority of insects, the life cycle of syrphids is little known and biological information is almost totally lacking. If the first accounts of Diptera having an agricultural, medical or veterinary importance have been well studied in Africa, the same thing cannot be said for Syrphidae. The only known larvae seem to be those of Ischiodon aegyptius, Paragus borbonicus, Sphaerophoria quadrituberculata, Ornidia obesa and Merodon bombiformis. Furthermore, Schmutterer (1974) published a list of a certain number of Syrphidae known as aphidiphagous from Kenya. A very large field of studies is thus offered up to African dipterists interested by the biological cycles and the ecological of the species.
We would like to warmly thank the following people who have very kindly put at our disposal the African syrphid collections of which they have charge: D. Azuma from the Academy of Natural Sciences of Philadelphia; E. De Coninck from the Musée Royal de l’Afrique Centrale, in Tervuren; P. Grootaert from l’Institut Royal des Sciences Naturelles de Belgique, in Brussels; L. Matile from Muséum National d’Histoire Naturelle, in Paris; H. Wendt from the Museum für Naturkende der Humboldt-Uyniversität, in Berlin. Our thanks also go to the Director of the Muséum d’Histoire naturelle de Genève, M.V. Mahnert who agreed to publish this Catalogue in the collection Instrumenta Biodiversitatis. We would also like to warmly thank our colleagues Daniel Burckhardt (Bâle), Jean-Paul Haenni (Neuchâtel) and Ivan Löbl (Genève) for the numerous improvements they have brought to the work, through their remarks and suggestions on the manuscript draft. Finally, we would like to recognise the memory of our friend and colleague Jean Steffen (Genève) who very kindly agreed to the thankless task of re-reading, in detail, the whole manuscript. The drawing of Allograpta nasuta habitat has been done by N. Lavoyer.
Notes for Use
This catalogue contains all species of dipteroid Syrphidae reported from the Afrotropical Region up to 1996. The sequence adopted is alphabetical for genera, the species are also cited by alphabetical order within each genus. The nomenclature follows, in general, the Catalogue of the Diptera of the Afrotropical Region (Smith & Vockeroth, 1980). We have made amendments according to the results of more recent studies (Hippa, 1985, 1990; Whittington, 1992) or due to critical examination of the literature. One will note through this work a certain number of new combinations, principally in the genera Lathyrophthalmus, Monoceromyia and Ceriana. With the Monoceromyia and Ceriana taxa we have compared the original descriptions of all the Afrotropical species to the distinctive generic characteristics listed by Shannon (1922) and Vockeroth & Thompson (1987) which has led to the proposal of a new arrangement of the genera in question.
Each reference to a specific taxa which is valid today or presently considered a synonym, comprises the following information: name, author(s) name, year of publication, book or periodical in which the name was published, page on which the name appears, place where taxa originates and finally the sex on which the description is based. This reference to the original description is followed by a group of citations of the taxa taken from the literature. The citations are comprised of the name of the author, the year, the publication in which the citation appeared, and the relevant page or figure in which the taxa in question appeared. The citations are always reproduced under the binomial that figures in the reference mentioned. The reader would thus have a complete insight into the successive generic attributes of various specific taxa. The books and periodicals in which the citations of Afrotropical syrphids figure are marked under an abridged form. For periodicals, the World List of Scientific Publications form was followed whereas for books, the titles were cited to conform to the current practice or following the rules applying to periodicals. You will find a complete reference to all publications, periodicals or not, in the bibliography at the end of this work. It was not judged to be useful to distinguish publications from the same author in the same year by particular symbols in the bibliography so all citations show the complete sources.
The Afrotropical Region, as defined for the needs of this publication, comprises the African continent to the south of the Sahara, the group of islands forming the Malgache Region, the islands of the Gulf of Guinea and Sainte-Hélène. The Yemen in Arabia is also included. The locality types are not systematically cited in the text, but the country of origin is always marked in the reference to the original description of each of the specific taxa. The distribution maps are marked with 73 species. They pick up on the localities where the taxa concerned are reported in the literature, including in some cases the material identified by the author. Particular care has been taken to precisely identify the localities listed in the various publications. To this effect a large number of atlas have been consulted, rounded off with an examination of Gazetteers and the perusal of expedition itineraries. In all more than 700 African localities have been listed in the literature. However it is not always easy to pin point towns and villages where the collecting took place. On the one hand historic authors didn’t show a great deal of concern for precision in their citations, and on the other hand numerous localities either no longer exist or have changed their name today. It follows that, despite an exhaustive research effort, it has not been possible to pin point all the collection localities. A closed spot characterises each locality that could be made in a precise manner. References that only concern one country, without precise localities, are represented on the maps by an open circle situated approximately in the centre of the country concerned. Finally, specimens seen and identified by the author are marked on the maps by a star. Where the species inhabit the islands of a region that isn’t featured on the maps, the names of the islands are marked in the bottom left hand corner of the maps.
The geographic distribution of taxa other than those that are the object of a map, are detailed in the brief text which follows the list of taxonomic references. This commentary summarises the distribution site as known today, placing the principal localities where each of the species is known. For several species, Smith & Vockeroth (1980) have marked a distribution complimentary to that raised in the literature, no doubt due to the examination of the collections. These data are shown in the text by a reference that makes mention of the “Catalogue”. It is worth noting that out of the 534 valid taxa itemised in this paper, 265 are only known from the locality type. The citation of localities, as with the countries, follows today’s usage and modern names are used throughout the text. All the names cited in the texts relative to geographic distribution figure, principally, in The Times Atlas of the World (comprehensive edition, 1988). We have maintained the designation of Zaire for the central African country formerly known as the Democratic Republic of Congo.
For syrphids inhabiting the island of Madagascar, an indication of the phytogeographic territories occupied is given. Following the works of Humbert (1955), one generally recognises Madagascar’s five large regions of vegetation as the following:
Domain of the east, corresponding to a band the length of the east coast and up until almost 800 m altitude;
Domain of the centre comprising notably the massifs of Ankaratra and Andringitra;
Domain from Sambirano to the north west of the island;
Domain of the West and
Domain of the South.
Some authors have added the Domain of the High Mountains, comprising the mountainous massifs situated above 2,000 m. You can find a map of these phytogeographic territories of Madagascar in Paulian (1961).