SIMULIIDAE OF AFRICA 31 



cibarium unarmed ; proboscis elongate, subequal to head-height. Claws with large basal tooth. 

 Gonapophyses simple rounded lobes. Pupa : Gill trifid, with long subequal tapering branches 

 (Text-fig. 223). Abdominal cuticle membranous and pale, cast pelt of pupa without brownish 

 sclerites (except for usual thickening on last segment). Terminal tubercles small, slightly 

 thorn-like. Abdominal onchotaxy normal (i.e. as usual basic plan in Simulium) ; all segments 

 dorsally without spine-combs. Cocoon delicate but discretely formed, shoe-shaped with simple 

 well defined anterodorsal rim, body of cocoon incorporating numerous small inorganic particles. 

 [Larva unknown.] 



Distribution. Known only from southern tip of African continent (Map 11), in 

 South Africa and Botswana (Bechuanaland). 



Discussion. Afrosimulium gen. n. is here erected for the single species gariepense 

 which de Meillon (1953), in the original description, suggested was probably closely 

 allied to Simulium griseicolle Becker because of the bare base- to the radius, and 

 presumably because of several other striking resemblances which, although not 

 strongly emphasized by de Meillon, it shares with griseicolle : these include the very 

 small size, fine dark lines of the female scutum, rather thick silvery vestiture of the 

 female, large claw-tooth, some resemblance in male hypopygium, and almost 

 identical pupa (the larva of gariepense is regrettably still unknown so that comparison 

 of this stage cannot be made). At first, these resemblances suggest convincing 

 evidence for postulating close affinity of gariepense with griseicolle, and therefore 

 that gariepense might be assignable to the subgenus Byssodon (syn. Psilocnetha) of 

 Simulium s.l., but a consideration of all the very extraordinary characters shown by 

 gariepense (and not mentioned by de Meillon) shows that the adult stage differs so 

 much from Simulium that assignment to this genus (even in its broadest sense) may 

 not be justified. It is necessary to discuss these characters in detail. 



The wings of gariepense when examined under the entomological microscope, i.e. 

 at magnifications up to x 100 or x 150, appear totally hyaline and bare instead of 

 showing the normal close speckling of dark microtrichia covering the wing mem- 

 brane ; gariepense therefore appears different (at these low magnifications) from 

 all other world Simuliidae, in which the microtrichial vestiture of the wing membrane 

 is obvious. The wings of gariepense are in fact closely covered, over the whole 

 membrane surface, with microtrichia but these are exceptionally minute (and also 

 rather blunt and twisted) as compared to those of other black-flies. The difference 

 in size between the normal microtrichia and the reduced microtrichia of gariepense 

 is shown by Plate iA & B, which are photographs at an approximate magnification 

 of x 40,000 taken by stereoscan microscope, of a part of the mid-wing microtrichial 

 vestiture in (A) Simulium damnosum with normal fully developed microtrichia, and 

 (B) Afrosimulium gariepense with the very reduced microtrichia. A. gariepense is 

 the only known Simuliid in which such vestigial microtrichia occur. 



By itself it would be inappropriate to attach much taxonomic significance to the 

 microtrichial reduction, which is a difference of degree rather than kind from other 

 black-flies, but gariepense also shows in the head of both sexes a form of sclerotic 

 architecture so completely different from that of all Simulium s.l. and almost all 

 other Simuliidae (there is a slight resemblance in the form of the occipital foramen 

 to some Gymnopais) that I consider it appropriate to place it in a genus of its own : 



