68 



R. W. CROSSKEY 



never occur in Eusimulium. A characteristic feature of the females of most 

 Pomeroyellum species is the reduction of pale scaling dorsally on the last few 

 abdominal segments, so that these appear rather bare, dark and shining : in this 

 character the subgenus resembles the Oriental subgenus Gomphostilbia Enderlein, 

 but Pomeroyellum differs from Gomphostilbia by having the katepisternum bare, 

 reduced number of parameral hooks, by the negative larval head-spots and the 

 presence of divided or scale-like setae on the larval abdomen, and it is unlikely that 

 there is any close phyletic relationship although Gomphostilbia and Pomeroyellum 

 clearly belong in the same general group of subgenera. 



Pomeroyellum may have some relationship with the subgenus Morops that is the 

 predominant component of the Simulium fauna in New Guinea and Australia. 

 Both subgenera include small forms with haired base to the radius, similar coxites 

 and styles, simple haired ventral plate, filamentous gills, dorsal spine-combs on 

 seventh and eighth pupal abdominal segments, and simple cocoons ; but 

 Pomeroyellum differs from Morops by having the pleural membrane and katepi- 

 sternum bare (both haired in Morops), by having one or more long strong parameral 

 hook each side in the male hypopygium (parameral hooks virtually absent in 

 Morops), and by the large female claw-tooth (absent or minute in Morops). 



The segregate of Simulium in the New World most closely resembling Pomeroy- 

 ellum is the subgenus Psilopelmia from Central and South America. Both subgenera 

 have slender fore tarsi, bare pleural membrane and katepisternum, essentially 

 similar male genitalia with similar range of form in the ventral plate, more or less 

 similar forms of filamentous or stoutly branched pupal gills, spine-combs dorsally on 

 the last few pupal abdominal segments, similar forms of cocoon, larvae with negative 

 head-spots and normally with well developed ventral papillae. The main differences 

 between Pomeroyellum and Psilopelmia are as follows : 



Subgenus POMEROYELLUM 

 (Ethiopian Region) 



Cibarium unarmed 



$ claw-tooth large 



<J paramere with one main hook and 



one or two smaller hooks 

 Basal section of radius haired 



Thorax dark, without definite 



pattern 

 $ paraprocts normal 



$ gonapophyses bluntly rounded, not 

 produced 



Subgenus PSILOPELMIA 

 (Neotropical Region) 



Cibarium armed with many small 

 pointed teeth between cornuae 

 (some exceptions) 

 $ claw-tooth small or absent 

 <$ parameral hooks numerous 



Basal section of radius bare or 

 haired 



Thorax often orange-coloured or 

 scutum with bold pattern 



$ paraprocts normally with lower 

 margin produced downwards, 

 often to fine attenuate point 



$ gonapophyses normally pro- 

 duced as long narrow flaps 



