io 4 R. W. CROSSKEY 



median sclerite toothed apically. Larval thorax bare, abdomen with sparse very minute divided 

 hairs and normal shape (without dorsal tubercles). Rectal gills without secondary lobules. 



At present the subgenus Edwardsellum contains three species ; two of these are 

 known only from Angola, but the other is Simulium damnosum Theobald, the most 

 serious man-biting Simuliid in tropical Africa and the main vector of human oncho- 

 cerciasis in Africa (Map 10 shows the distribution of this important vector species 

 since it occurs in all localities for which the black circle symbols are shown). The 

 number of species in Edwardsellum may be much increased as the result of current 

 and future work on 5. damnosum, since it is possible (and by some workers regarded 

 as already proven) that this species is a complex of sibling species, some of which are 

 primarily anthropophilic and others non-anthropophilic — a difference in feeding 

 habits with a direct bearing on the transmission of human onchocerciasis, and there- 

 fore of more than academic interest. Particularly clear-cut distinctions in feeding 

 habits exist in different localities of S. damnosum in Uganda, anthropophily being 

 the norm in some and non-anthropophily in others, and Dunbar (1966) claims that 

 at least four sibling species are represented in the ' S. damnosum ' populations of 

 Uganda : names available in nomenclature have not been given to the different 

 sibling segregates, but Dunbar correctly points out that the restricted name 

 damnosum would apply to the anthropophilic form occurring in the Victoria Nile 

 near Jinja whence the type-material of damnosum originated. 



Dunbar's sibling species have been distinguished solely on cytological differences 

 found in the giant polytene chromosomes of the salivary glands of 5. damnosum 

 larvae from different locations, each sibling being recognized by inversions imposed 

 on the same basic banding pattern sequence ; the characters used in differentiating 

 the siblings are micromorphological ones, the genetical significance of which is 

 uncertain. No experimental evidence exists to support the supposition that the 

 cytologically distinguishable entities (of which nine are now known from different 

 parts of Africa) within S. damnosum are biologically distinct species, and it may be 

 premature to assume that they are. So far the various components of S. damnosum 

 have been shown to differ only in the larval chromosome characters, and no corre- 

 lated differences have yet been demonstrated in external larval characters or in the 

 morphology of other stages. Nonetheless the subgenus Edwardsellum must be 

 looked upon as composed of a minimum of three species, with the possibility or 

 likelihood that several others exist : if so it is possible that Enderlein's names 

 applied to S. damnosum may be recovered from synonymy. 



Included taxa. Simulium {Edwardsellum) damnosum Theobald and associated 

 supposed sibling species, at present unnamed (see above) ; S.(E.) machadoi Luna de 

 Carvalho ; S.(E.) vilhenai Luna de Carvalho. 



Subgenus TE TISIM UL I UM Rubzov 



Tetisimulium Rubzov, 1963 : 497. Type-species: Melusina bezzii Corti, 1914, by original 

 designation. 



Diagnosis. 5*$ : Basal section of radius bare. Pleural membrane haired. Katepisternum 



