38 R. W. CROSSKEY 



13 Ventral plate with well developed shoulders and parallel basal arms, haired across 



most of width of apical margin (Text-fig. 104), plate only slightly curved in 

 profile (Text-fig. 129). Style not abruptly truncate (Text-fig. 148). [Malagasy 

 Region only] XENOSIMULIUM sgen. n. (p. 86) 



— Ventral plate with more sloping shoulders, or subtriangular (Text-figs. 108, 109) in 



profile body of plate strongly bent or angulate in relation to basal arms (Text-fig. 

 132). Style rather truncate apically (Text-fig. 149). [Ethiopian Region only, 

 including southern Arabia] .... ANASOLEN Enderlein (p. 88) 



14 Basal section of radius bare. Styles long and heavy, conspicuous in situ, sub- 



parallel-sided and very much longer than coxites (Text-figs. 94, 155) ... 15 



- Basal section of radius haired. Styles shorter than or at most subequal in length to 



coxites ............. 17 



15 Pleural membrane bare ..... SIMULIUM Latreille s. str. (p. no) 



— Pleural membrane haired .......... 16 



16 Fore tarsus slender, basitarsus 7-8 times as long as its greatest breadth (Text-fig. 



85). Ventral plate Y-shaped, in profile without beak-like projection (Text-fig. 



138) TETISIMULIUM Rubzov (p. 104) 



- Fore tarsus flattened and dilated, basitarsus 4-5-5 times as long as its greatest 



breadth (Text-figs. 86). Ventral plate as Text-fig. 119, in profile with haired beak- 

 like projection (Text-fig. 139) . . . ODAGMIA Enderlein (p. 107) 



17 Pleural membrane bare. Ventral plate broad lamellate (Text-figs. 100, 101) with 



subparallel basal arms (except in aureum-group with small triangular plate and 

 divergent arms, Text-fig. 102). Style not folding down against coxite. Only one 

 main parameral hook on each side. . . EUSIMULIUM Roubaud (p. 56) 



— Pleural membrane haired. Ventral plate subtriangular with large divergent basal 



arms (Text-figs. 93, 113). Style very small and capable of folding down against 

 large coxite (Text-fig. 151). Parameral hooks numerous (Text-fig. 93) 



WILHELMIA Enderlein (p. 94) 



Females 



1 Forms from Ethiopian and Malagasy Regions ....... 2 



- Forms from North Africa and Canary Islands . . . . . . . 13 



2 Basal section of radius bare .... BYSSODON Enderlein (p. 44) 



- Basal section of radius haired .......... 3 



3 Head abnormal, eyes small and in profile only a little wider than postocular part of 



head (Text-fig. 69), in dorsal view frons almost as wide as one eye (Text-fig. 71). 



[St. Helena Island only] DEXOMYIA sgen. n. (p. 49) 



— Head normal, eyes occupying most of sides of head and frons conspicuously narrower 



than one eye in dorsal view (Text-figs. 66, 70). [Not from St. Helena, except one 

 species of Eusimulium] .......... 4 



4 Katepisternum haired. Ground colour of thorax reddish to dark red-brown. Gona- 



pophyses fleshy and protruberant downwards, paraprocts also slightly or strongly 

 produced ventrally (Text-fig. 163) . . FREEMANELLUM sgen. n. (p. 92) 



— Katepisternum bare. Ground colour of thorax almost always blackish. Gona- 



pophyses and paraprocts not so ........ . 5 



5 Fore tarsi conspicuously dilated and with thick dorsal hair-crest (Text-figs. 81, 82), 



basitarsus 3 -5-5 times as long as its greatest breadth ...... 6 



- Fore tarsi not enlarged and flattened and without conspicuous hair-crest (Text-figs. 



78-80), basitarsus usually 5-5-8 times as long as its greatest breadth ... 7 



6 Hind basitarsus creamy white on most of its length and contrasting conspicuously 



with black remainder of tarsus. Gonapophyses forming slender curled acuminate 

 processes (Text-fig. 159). Spermatheca with long internal hairs. Scutum with 



