i 4 R. W. CROSSKEY 



supposedly more primitive forms and the Simuliini containing the supposedly more 

 specialized forms (in which, among other features, there has been a reduction of 

 hairing on the radius, the development of a pedisulcus, increasing complexity with 

 development of teeth on the male ventral plate, development of a discrete cocoon). 

 No hard and fast line can be drawn between the two tribes, and no single character 

 exists that will hold for distinguishing every form in one tribe from every form in the 

 other ; nevertheless, on total suites of characters there is a definite and apparently 

 natural cleavage between two major aggregations of forms, and Prosimuliini and 

 Simuliini are the nomenclaturally correct names to apply to the two taxa ranked at 

 tribal level. Full diagnoses for the two tribes are given later in this paper. 



In the area of Africa and its islands falling within the purview of the present 

 revision four genera of Simuliidae occur, of which one is placed in the Prosimuliini 

 and three in Simuliini. The Prosimuliine genus Crozetia Davies from the Crozet 

 Islands in the South Indian Ocean is excluded from consideration as it is an element 

 of the sub-Antarctic fauna having no affinity at all with any forms in the Malagasy 

 Region. A key to the four genera is given below. 



Keys to the Genera of Simuliidae in Africa and its Islands 



Adults 



i Pedisulcus absent. Basal cell present, usually quite distinct (Text-fig. i). Costa 

 sometimes without spiniform macrotrichia. Basal section of radius always haired. 

 Katepisternum in profile about as deep as its length, delimited by rather broad 

 mesepisternal sulcus, the sulcus often evanescent anteriorly (Text-figs. 16, 18) . 2 



- Pedisulcus present. Basal cell absent. Costa with spiniform macrotrichia as well 



as hairs. Katepisternum in profile longer than its depth (Text-fig. 19), delimited 



by a deep narrow and more or less complete mesepisternal sulcus (Text-fig. 17) . 3 



2 Pleural membrane haired. Style of o* hypopygium with one apical spinule. Calcipala 



undeveloped. Costa with spiniform macrotrichia and vein Rs simple. [North 

 Africa] METACNEPHIA gen. n. (p. 26) 



- Pleural membrane bare (but in morotoense a few hairs present on upper mesopleuron j ust 



below scutal ridge.) Style of o* hypopygium with multiple apical spinules (number- 

 ing 3-9, Text-figs. 31-33). Calcipala often moderately developed (Text-figs. 23- 

 25). Costa sometimes without spiniform macrotrichia and sometimes with Rs 

 forked. [North Africa and Ethiopian Africa] . PROSIMULIUM Roubaud (p. 17) 



3 Calcipala present, very well developed. Wing membrane with normal microtrichia 



(Plate iA), easily visible at X 100. Last segment of maxillary palp long and 

 slender, much longer than preceding segments (Text-figs. 69). Posterior surface of 

 head normal (Text-figs. 57, 59), postgenal membrane narrow and postgenal lobes 

 angulate at ventral edge of foramen, continuous sclerotization between cardines. 

 Basal section of radius haired or bare. [Widespread throughout area]. 



SIMULIUM Latreille (p. 34) 



- Calcipala almost absent (Text-fig. 306). Wing membrane with extraordinarily 



reduced microtrichia (Plate iB), wing surfaces appearing totally bare at magnifica- 

 tions of X 100 or X 150. Last segment of maxillary palp not longer than either of 

 the two preceding segments (Text-fig. 305). Posterior surface of head abnormal 

 (Text-figs. 58, 60), postgenal membrane broad and postgenal lobes not sharply 

 angulate near lower corners of occipital foramen, head widely membranous be- 

 tween the cardines. Basal section of radius bare. [Southern Africa only] 



AFROSIMULIUM gen. n. (p. 30) 



