SIMULIIDAE OF AFRICA 103 



Group I, Sub-group B, particularly S. nebulicolum Edwards, S. iridescens de Meijere, 

 and S. nobile de Meijere ; these forms have a dilated fore tarsus and a bold black 

 and grey pattern to the male scutum, but the basal section of the radius is bare and 

 the male hypopygium is of the type found in Simiilium s. str., and there is clearly no 

 close relationship between them and Edwardsellum. Although the Oriental 

 Simulium fauna has not been studied in detail it is certain that most of the species in 

 this region that lack hairs on the base of the radius and have heavy elongate male 

 styles are assignable to the subgenus Simulium s. str., and that they have little or 

 no relationship with the Afro-Palaearctic group of subgenera associated with 

 Wilhelmia (in which Edwardsellum clearly fits). 



The characters of the pupa, the larval head, the male genitalia and the gonapo- 

 physes of the female terminalia all closely resemble those of the subgenus Metom- 

 phalus, and to a lesser extent of Wilhelmia, and the phyletic affinities of Edwardsellum 

 lie with these subgenera. Freeman & de Meillon (1953) placed Simulium damnosum, 

 the type-species of Edwardsellum, in their medusaeforme-group (the typical group of 

 the subgenus Metomphalus) and it would be possible to regard the species of 

 Edwardsellum as constituting a species-group in the same subgenus as the medusae- 

 forme-group and the bovis-group. If this course was adopted the valid name for the 

 composite subgenus so recognized would be Edwardsellum Enderlein, 1921 (with 

 priority over Metomphalus Enderlein, 1935). However, it appears preferable to 

 rank Edwardsellum and Metomphalus as separate subgenera because of the major 

 differences in the larval and adult stages, especially as it would be difficult to 

 formulate any satisfactory diagnosis of the resultant group if the two concepts were 

 merged. 



Both the subgenera Edwardsellum and Metomphalus are closely related to Wilhel- 

 mia, as is especially evident from the pupal stage (cf. gill form, especially the basal 

 arms, in Text-fig. 207 with that in Text-figs. 209, 210 and 212), but not so closely as 

 to justify the synonymy of the three names : for a balanced classification on a world 

 basis the two Ethiopian subgenera require to be maintained as named entities, 

 equivalent in rank to the Palaearctic subgenus Wilhelmia. I therefore do not follow 

 Stone (1963 : 6, 12, 22) in treating the names as synonyms, or Rubzov (1962 : 

 1500-1501) in treating Edwardsellum as a full genus to include all the species here 

 placed in the subgenus Metomphalus as well as those placed in Edwardsellum, but 

 prefer to recognize three segregates of equal subgeneric status. Distinctions between 

 Metomphalus and Wilhelmia are discussed under Metomphalus : the following 

 summary of characters shows the main differences between Edwardsellum and 

 Wilhelmia : — 



Edwardsellum. Pleural membrane bare. Tarsal claws of $ toothed, not enlarged. Scutum 

 of o* with black and silver-grey pattern, scutum of $ bluish black with very indistinct dark lines. 6" 

 ventral plate toothed, complex shapes ; median sclerite not toothed apically. Larval thorax 

 and abdomen with vestiture of simple scales ; first five abdominal segments with paired dorsal 

 tubercles. Rectal gills with secondary lobules. 



Wilhelmia. Pleural membrane haired. Tarsal claws of $ simple, greatly enlarged. Scutum 

 of o* without bold black and grey pattern, scutum of $ pale greyish with conspicuous dark lyrate 

 mark (Text-fig. 72). o* ventral plate not toothed, excavate-subtriangular (Text-fig. 113) ; 



