172 



R. W. CROSSKEY 



283 



'MP 



286 



285 



288 



290 



Figs. 283-290. Larval characters of African Simulium. 283, dorsal view of head in sub- 

 genus Lewisellum showing shape of cephalic apotome and negative pattern. 284, body 

 shape in profile in subgenus Lewisellum. 285, apex of abdomen in subgenus Phoretomyia 

 showing ventral orientation of posterior circlet. 286, dorsal view of head in copleyi- 

 group of subgenus Phoretomyia showing straight ' cut-off ' cephalic fans. 287, profile of 

 unusual body shape in albivirgulatum-group of Metomphalus. 288, antenna of forms with 

 short third segment. 289, antenna of forms with long slender third segment. 290, 

 antenna in subgenus Xenosimulium, showing secondary annulation. 



