A pictorial guide to the chromosomal identification of members of the Simulium damnosum Theobald complex in west Africa with particular reference to the Onchocerciasis Control Programme Area.

Simulium damnosum Theobald is made up of a complex of sibling species. Nine species are described in the area covered by the World Health Organisation's Onchocerciasis Control Programme in West Africa (OCP). These are, S. squamosum, S. yahense, S. canctipauli, S. soubrense, S. leonense, S. konkourense, S. damnosum s.s., S. sirbanum and S. dieguerense. All of them are vectors of human onchocerciasis, albeit to different capacities. Reliable species determination presently depends on larval cytotaxonomic criteria. The diagnostic chromosomal inversions and other micromorphological characters used in the identification of the species found in the OCP area are presented with figures for their recognition, some distributional information is also given.