SIMULIIDAE OF AFRICA 75 



blunt and inconspicuous. Accessory sclerites present but sometimes only minute weakly 

 sclerotized trace. Rectal scales present. Rectal gills with secondary lobules, sometimes small 

 and very few or one lobe simple. Posterior circlet usually with 70-80 rows of 8-15 hooks. 



Bionomy. Eggs clustered, adhered to substrate. Larval and pupal stages non- 

 phoretic ; attached to varied substrates but mainly trailing herbage in wide variety 

 of stream and river habitats, including rapids and large sandy-bedded rivers ; 

 immature stages recorded from unusual ecological habitats of lacustrine wave- 

 action and brackish estuarine waters. Female occasionally anthropophilic, probably 

 normally ornithophilic. 



Distribution. Confined to, and widespread in, the Ethiopian Region (Map 4) 

 excluding southern Arabia. 



Discussion. Rubzov (1962) erected the genus Meilloniellum for the species placed 

 by Freeman & de Meillon (1953) in their hirsuttim-gvoup, with Simulium hirsatum 

 Pomeroy as type-species. The segregate is here accepted as valid with subgeneric 

 status, but in a more restricted sense than that of Rubzov. The subgenus here 

 defined contains only the small free-living forms previously placed in the hirsutum- 

 group, and excludes all those Ethiopian Simulium in which the larval and pupal 

 stages live in obligate phoresis with crabs or nymphal mayflies : the phoretic forms 

 are best placed in separate subgenera for the reasons discussed under the names 

 Lewisellum sgen. n. and Phoretomyia sgen. n. 



I agree with Rubzov that hirsutum and its immediate allies are best placed in a 

 genus-group segregate distinct from Pomeroyellum, but it must be admitted that it 

 is difficult to formulate differential diagnoses that are completely adequate for 

 distinguishing Meilloniellum from Pomeroyellum at all stages. The two subgenera 

 are probably closely related, since they have in common the following characters : 

 basal section of radius haired, large claw-tooth in female, similar female terminalia, 

 scutum of both sexes without pattern, non-dilated fore tarsi, haired ventral plate, 

 one main parameral hook in each parameral organ, short styles, simple slipper- 

 shaped cocoon and same type of filamentous pupal gill, similar pupal abdominal 

 armature, larvae with negative head pattern and similar mandibles. 



The pupal stages of Meilloniellum and Pomeroyellum are subgenerically inseparable, 

 but other stages show the following distinctions : $ abdomen thickly covered with 

 silvery or silver-yellow scales in Meilloniellum (posterior part normally bare and 

 shining in Pomeroyellum although a few species with complete thick vestiture) ; 

 <$ style abruptly contracted before the end, and terminal third bearing the spinule 

 attenuated (never of this form in Pomeroyellum) ; <$ ventral plate in Meilloniellum 

 with broad deep median apical notch (without such emargination in Pomeroyellum) ; 

 larval abdominal cuticle posterodorsally with minute simple setae in Meilloniellum 

 (i.e. not with complex divided setae, flattened scales or bare as in Pomeroyellum). 



From Eusimulium, to which there is undoubtedly a general relationship, Meilloni- 

 ellum is distinguished by the negative larval head pattern, shape of the male styles, 

 and to a lesser extent by the shape of the ventral plate. The characters separating 

 the subgenus from Lewisellum and Phoretomyia are enumerated elsewhere in the 



