72 R. W. CROSSKEY 



groups it would make the resultant group much less homogeneous and more difficult 

 to diagnose satisfactorily. They are therefore placed here as a small group of their 

 own, coming between the alcocki-group and the cervicornutum-group. The existence 

 of this intermediate group, with larvae like those of cervicornutum but pupae like the 

 alcocki-group, confirms that — despite the striking difference in pupal gill form — the 

 alcocki-group and the cervicornutum-group should be treated as consubgeneric ; 

 the alcocki-group is therefore assignable to subgenus Pomeroyellum. 



The form of the male ventral plate in the species of schoutedeni-group is slightly 

 closer to that in cervicornutum-group than alcocki-group. 



Included taxa. Simulium {Pomeroyellum) mcmahoni de Meillon ; S.(P.) schou- 

 tedeni Wanson. 



cervicornutum-group. q* hind basitarsus normal, slender ; styles normal ; ventral plate 

 with well developed shoulders, excavate laterally (Text-fig. 99), slender or slightly thickened in 

 profile. Pupal gill not filamentous, of large bladder-like or branched antler-like form variously 

 modified (Text-figs. 187-192). Cocoon without neck. Larval abdomen with large sparse erect 

 scale-like setae, dark and conspicuous, and with accessory sclerites. Larval postgenal cleft 

 large and much longer than postgenal bridge, mitre-shaped. 



S.(P.) cervicornutum Pomeroy is type-species of Pomeroyellum and this is the 

 typical group of the subgenus nomenclaturally ; it contains all the species of 

 Pomeroyellum in which the pupal gill is not of the filamentous type. The group is 

 widespread in the Ethiopian Region and one species, S.(P.) pauliani Grenier & 

 Doucet, is found in Madagascar. The cervicornutum-group, more than any other 

 group of Pomeroyellum, is adapted to live in a variety of fluvial habitats from 

 slowly-flowing weedy streams to broken fast waters in large rivers, occasionally even 

 in mountain cascades, and the immature stages of cervicornutum itself may be found 

 in a wider variety of situations than those of any other Ethiopian Simuliid ; even 

 unicornutum Pomeroy, although habitually occupying small-stream habitats, 

 sometimes occurs in the rapids of large rivers. 



The larvae of the group can be recognized at once among mixed collections of 

 black-fly larvae from the Ethiopian Region by the characteristic large blackened 

 and erect scales standing sparsely on the posterodorsal part of the abdominal 

 cuticle, and readily seen with low-power magnification. Apart from similar vesti- 

 ture in larvae of the related schoutedeni-group (see above), such arrangement of large 

 sparse scales appears to be unique among the larvae of world Simulium. In addition 

 to the scales, the abdomen of cervicornutum-group larvae is rather distinctive 

 because of the presence of a pair of small accessory sclerites (one each side of the last 

 segment immediately before the circlet : Text-fig. 224) and of an unusually dark 

 annular mottling on the segments ; in addition the mediodorsal parts of the first 

 four or five segments are often rather prominent (sometimes even tending towards 

 the development of tubercles recalling those of Edwardsellum larvae). 



The pupal gill in this group assumes a variety of forms that is probably more 

 diverse than in any other segregate of Simuliidae, with the possible exception of the 

 Nearctic and northern Neotropical subgenus Hearlea Vargas, Martinez Palacios & 

 Diaz Najera in which a somewhat similar bizarre range of form occurs (figured, for 



