SIMULIIDAE OF AFRICA 79 



west, and no adult Simuliidae assignable to the subgenus have been found in West 

 Africa ; it is probable that this is a genuine fact of distribution, and not an artifact 

 from inadequate knowledge. It is possible that the subgenus evolved in the Rift 

 Valley region of eastern Africa with subsequent westward dispersal to the Congo 

 Basin and Cameroon. 



Included taxa. Simulium (Lewiselhim) goinyi Lewis & Hanney ; S.(L.) hightoni 

 Lewis ; S.(L.) neavei Roubaud ; S.(L.) nyasalandicum de Meillon ; S.(L.) ovazzae 

 Grenier & Mouchet ; S.(L.) woodi de Meillon. 



Subgenus PHORETOMYIA sgen. n. 



Type-species : Simulium copleyi Gibbins, 1941. 



Diagnosis, o*? : Basal section of radius haired. Pleural membrane bare. Katepisternum 

 bare. Fore tarsus usually strongly dilated and with short dorsal hair crest, fore basitarsus 4-5 

 times as long as its greatest breadth (except berneri in which 6-7 times longer than broad). $ : 

 cibarium unarmed. Tarsal claws with medium size to large basal tooth, rarely small and blunt. 

 Scutum without pattern or with broad median longitudinal dark band flanked by paler lateral 

 areas. Abdomen very thickly covered with pale yellow to golden scales on first two segments, 

 other segments mainly with dark or scattered patches of pale scales, terminal segments some- 

 times shining and with sparse hairs only. Seventh sternite at least weakly developed. Gona- 

 pophyses simple bluntly rounded lobes. Paraprocts normal. Spermatheca without or with 

 weak traces of polygonal pattern, without internal hairs, o* : scutum as in female. Genitalia 

 with small styles shorter than coxites, style curved subconical and with one apical spinule ; 

 coxite not produced beyond base of style ; ventral plate not toothed, large but longer than its 

 width with rounded shoulders, very small forwardly directed basal arms, at least a trace of 

 median apical emargination, and usually with a small median notch in the anterior margin 

 between the basal arms (Text-fig. 106) ; median sclerite long and slender, parallel-sided, strap- or 

 rod-like; parameres narrow and irregular, with one long strong parameral hook (sometimes with 

 small supernumerary hook at its base), or without definite hook but with a small slender irregular 

 terminal process. Pupa : Gill with very slender thread-like filaments, numbering from 10-95, 

 mainly arising individually near base, when filaments very numerous, gill assuming semicircular 

 shape (Text-figs. 198 & 199) ; gill normally shorter than pupal body. Abdominal onchotaxy 

 varied, sometimes with normal basic hook plan plus a pair of hooklets ventrally on segment 4, 

 sometimes aberrant and some segments showing supernumerary hooks dorsally, or segments 5-8 

 girdled with supernumerary blunt booklets ; terminal segments dorsally without spine-combs. 

 Cocoon a simple pocket without neck or median projection, often shorter than normal and some- 

 times covering only the abdomen or abdomen and posterior third of thorax. Larva : Aberrant 

 from typical Simulium in many characters. Head shape usually atypical, sides often strongly 

 convex and cephalic apotome broadest near or slightly behind the middle and contracting 

 thence towards hind margin of head (Text-fig. 286) ; cephalic fans either normal or aberrant, in 

 latter case forming when open a short flat brush of almost straight or slightly sinuous rays curved 

 only at the tips. Hypostomium atypical in older and mature larvae, of varied forms (Text-figs. 

 265-267) ; hypostomial setae 3-7 in each row, sometimes irregular, rows lying parallel to 

 lateral margins of hypostomium. Head-spots indefinite, cephalic apotome lightly pigmented 

 and usually with trace of paler negative spots, sometimes spots apparently darker than surround- 

 ing areas, occasionally head suffused with dark pigmentation on posterior half of cephalic 

 apotome and on bulbous lateral areas. Postgenal cleft absent so that whole floor of head is 

 sclerotized (Text-fig. 252), or at most represented by shallow inconspicuous usually subrect- 

 angular notch, postgenal bridge therefore virtually continuous to hind margin of cranium. 



