SIMULIIDAE OF AFRICA 



169 



257 



258 



259 



260 



261 



262 



264 



265 



266 



267 



268 



Figs. 257-268. Form of the postgenal cleft (257-264) and of the hypostomium (265-268) 

 in mature larvae of African Simulium. 257 and 258, Metomphalus, medusaeforme- 

 group. 259, Metomphalus, albivirgulalum-group. 260, Metomphalus, bovis-group. 

 261, Edwardsellum. 262, Byssodon. 263, Teti simulium. 264, Odagmia. 265, Phoreto- 

 myia, lumbwanum-gr oup. 266, Phoretomyia, copley i-group. 267, Phoretomyia, berneri- 

 group. 268, Lewisellum. (Figures 265-268 illustrate the hypostomium in phoretic 

 forms.) 



