22 R. W. CROSSKEY 



tooth. Gonapophyses of $ terminalia as in Paracnephia (Text-fig. 34). Pupal abdomen with- 

 out large pleural plates on sides of segments 4 and 5, terga and sterna of these segments separated 

 by a single longitudinally striate area with at most only minute platelets. Pupal gill with six or 

 seven filaments, convergent at the tips. Ventral plate of o* flattened, without lip, slender in 

 profile (Text-figs. 26, 27). Style of o* curved and excavate on inner side (Text-fig. 31), sometimes 

 longer than coxite. Larval hypostomium with outermost tooth of each outer group always 

 shorter than main tooth of outer group (Text-figs. 49, 50). Larval mandible with irregular saw- 

 like series of about 10-16 serrations, sometimes apparently only a few and very blunt (but this 

 probably due to wear or damage). 



Bionomy. [Oviposition habit unknown.] Larvae and pupae attached to rock 

 surfaces or lithophilic mosses in fast water, sometimes in closely aggregated masses, 

 in streams subject to periodical drying ; cocoons sometimes very weakly differen- 

 tiated and pupae in almost common silk network, mature larvae apparently in this 

 case migrating to common pupation ground (de Meillon & Hardy (1951)). [Biting 

 preferences of forms with fully developed female mouthparts unknown ; female 

 mouthparts sometimes partially atrophied and presumed non-functional, therefore 

 such forms autogenous.] 



Distribution. Known distribution very sparse and scattered (Map 1), recorded 

 from South-West Africa, South Africa, Rhodesia and Uganda. 



Discussion. The subgenus Procnephia is here erected, with P. rhodesianum 

 Crosskey as type-species, for a small number of species that I have elsewhere referred 

 to as the damarense-gvoup (Crosskey, 1968). These species are difficult to place 

 satisfactorily in a classification that looks at world forms since their characters 

 almost completely interlink those of true Holarctic Prosimulium with those of 

 Paracnephia, a segregate rather weakly defined by Rubzov (1962) that he proposed 

 for the inclusion of all the primitive southern African black-flies previously placed by 

 Freeman & de Meillon (1953) in the genus Cnephia. If the intermediate species here 

 constituting the new subgenus Procnephia are assigned arbitrarily to either Pro- 

 simulium or Paracnephia it makes the resultant group very difficult to define, and I 

 think it better to treat them as a small subgenus on their own, ranked equivalent to 

 Paracnephia and placed in sequence between Prosimulium s. str. and Paracnephia 

 (in the more restricted sense in which this segregate is now defined). Even so, it 

 cannot be claimed that any of the three subgenera can be entirely satisfactorily 

 delimited, and it is the existence of these " awkward " intermediate forms in 

 Ethiopian Africa (there are others in Australia, southern South America and 

 northern Central America) that convinces me that it is essential to re-define Pro- 

 simulium more broadly than in the past and to incorporate into it, as subgenera, a 

 range of forms that overlap so closely in their characters with Prosimulium in the 

 strict sense that no clear generic distinctions can be maintained. 



Procnephia has the costa and radial veins entirely hairy as in Prosimulium s. str. 

 but has more or less lost the clear bifurcation of Rs (assuming as usual that a more 

 complete venation is ' primitive ') : even in this character, however, the distinction 

 is not absolute, for some specimens of Procnephia (if the wing is carefully examined) 

 show clear traces of doubling at the extreme tip of Rs and may show a parting into 

 two irregular rows of the hair vestiture, which may fairly be interpreted as the last 



