io R. W. CROSSKEY 



present. In the case of the islands black-flies are absent from those which are 

 devoid or almost devoid of running water (Ascension, Tristan da Cunha, Aldabra) 

 but are abundant — though very limited in number of species — in those which are 

 well-watered by numerous cascading streams (St. Helena, Seychelles, La Reunion). 

 (How the Simuliidae have reached such remote islands can only be conjectured but 

 it is notable that the forms that have done so almost all possess a large tooth basally 

 on the claws of the female, characteristic of ornithophilic species : carriage on birds 

 is the most plausible explanation, though we lack evidence that black-flies can survive 

 for more than a very brief period on avian hosts.) 



CHARACTERISTICS AND AFFINITIES OF THE SIMULIID FAUNA OF THE 

 ETHIOPIAN AND MALAGASY REGIONS 



The Simuliid fauna of North Africa and the Canary Islands is entirely typical for 

 the Palaearctic Region, and is therefore only very briefly considered further below, 

 but a more detailed review of the main zoogeographical features and possible 

 affinities of the Simuliidae of the Ethiopian and Malagasy Regions is given in order 

 to show how the fauna of these regions fits in the world picture (and to assist workers 

 in other areas to whom a digest of the principal characteristics of the African fauna 

 might be useful for comparative purposes). 



All genus-group taxa and many of the species in North Africa are shared in common 

 with the Simuliid fauna of western Europe, and most with the Canary Island fauna 

 also : the best represented segregates are Eusimulium, Wilhelmia and Odagmia. 

 Only one species found in North Africa occurs also in the Ethiopian Region : this 

 is Simulium (Eusimulium) ruficorne with the widest distribution of any African 

 black-fly, occurring through North Africa (Morocco to Tunisia), in Egypt and 

 Middle East, the whole Ethiopian Region (including southern Arabia), and the 

 Malagasy Region including the Mascarene islands ; the Palaearctic and Ethiopian 

 distributions of ruficorne are interlinked by the occurrence of this species in the mid- 

 Sahara massifs of Tibesti and Tassili des Ajjer, and it is impossible to be certain 

 whether ruficorne is to be seen as a Palaearctic species that has spread throughout 

 the other regions or as an Ethiopian element that has penetrated into the southern 

 Palaearctic Region. 



The Malagasy Region (including the Seychelles and Mascarene islands) has a very 

 limited Simuliid fauna in which the more primitive Prosimuliini are, so far as is 

 known, completely absent and in which three subgenera of Simulium s.l. are the 

 only genus-group taxa represented : of these Eusimulium is almost cosmopolitan, 

 Pomeroyellum is an Ethiopian segregate that has clearly reached Madagascar from 

 the African mainland, and the third (Xenosimulium sgen. n.) is endemic, but has 

 many characters in common with two of the subgeneric segregates in the Ethiopian 

 Region and may have derived also from forms that originated from Africa. One 

 species in Madagascar (starmuhlneri) has characters resembling some forms of 

 Morops from New Guinea, but convergence is presumed, and there is no evidence of 

 close affinity between the Malagasian fauna and that of the Oriento-Australasian 

 Regions : the endemic subgenus Xenosimulium sgen. n. shows many resemblances 



