SIMULIIDAE OF AFRICA 85 



with thick pale yellow or golden scaling on first two segments, and some pale scales laterally and 

 intermixed dorsally with bronze-black scaling, terminal segments dorsally with sparse black 

 hairs and semi-shining, q* hypopygium without properly formed parameral hooks (except 

 diceros), these represented by small irregular process on end of each paramere. Pupal gill with 

 10-40 filaments, most often 17 (Text-fig. 197). Pupal abdomen with a normal basic onchotaxy 

 supplemented by some supernumerary hooklets as follows : two hooklets each side ventrally on 

 segment 4 (Text-fig. 172), a row of four or seven minute spinous hooklets each side dorsally on 

 segments 3 and 4 (so that there are seven hooks each side on these segments in place of the 

 normal four. Text-fig. 169), sometimes also two or three spinous hooklets each side latero- 

 dorsally on segment 5. Cocoon reduced, covering only pupal abdomen or at most posterior part 

 of thorax also. Larval head aberrant, sides bulbous and strongly convex, cephalic apotome 

 widest near middle and contracting towards hind margin (Text-fig. 286) ; cephalic fan when 

 open forming short flat brush, rays broad for most of their length then abruptly narrowed and 

 slender at curved tips. Larval antenna conspicuous, slightly shorter than stem of cephalic fan, 

 three-segmented through obliteration of first suture or four-segmented. Hypostomium with 

 apical row of thirteen teeth, all or mostly rather blunt or rounded, formed from usual nine with 

 outer two serrations on each side enlarged and produced forwards (as in Text-fig. 266 or with 

 teeth shorter and blunter than this.) Larval mandible with main apical tooth very large and 

 other apical teeth short and blunt, without mandibular serrations (though inner edge of mandible 

 irregularly formed), comb-teeth very small or exceptionally minute (Text-fig. 299). Larval 

 cuticle bare. Apex of abdomen as in Text-fig. 285. 



The copleyi-group includes species in which the larval head has the most aberrant 

 form found in any African Simuliidae, not only in the convexity and Prosimuliine- 

 like shape of the cephalic apotome but in the form of the cephalic fans ; these, 

 instead of the normal curved basket-like feeding brushes found in the vast majority 

 of black-flies, have when open a flat subtriangular fan shape. The rays composing 

 this flat fan, instead of being sickle-shaped, are mainly straight or slightlysinuousand 

 relatively broad on most of their length, tapering abruptly to a fine curved tip on 

 about the apical sixth ; the fine filter apparatus is very difficult to see and is con- 

 fined to the slender tips of the rays only. At present it is uncertain what adaptive 

 function is subserved by this exceptional modification to the normal mouth-brush, 

 which is made the more puzzling by the fact that S.(P.) lumbwanum — which occurs 

 in an apparently similar phoretic environment attached to the same genus of may- 

 flies — has the usual form of hemispherical brush. 



The copleyi-group species live in association with species of Afronnnis Lestage 

 (Heptageniidae) and Baetis Leach (Baetidae), and have also been found attached to 

 nymphs of generically unidentifiable Baetids. It is not known how many and 

 which species of mayflies are involved in phoretic associations with the group 

 because of the difficulties of identification of African mayfly nymphs to the specific 

 level, but in the genus Afronurus at least the species A. negi Corbet is concerned 

 (Corbet, 19606 : 71) and almost certainly several others. The distribution of the 

 copleyi-group appears to be centred mainly in East Africa and eastern Congo, but a 

 species (rickenbachi) has recently been described from the Kumbo area of West 

 Cameroon (Germain et al. 1966). 



The poorly known species S. diceros Freeman & de Meillon is assigned here to the 

 cc^>/<?yz-group, to which it fits on its pupal characters and choice of phoretic partner ; 

 but it should be emphasized that the slender fore tarsus, well formed parameral hook, 



