SIMULIIDAE OF AFRICA 97 



normal. Spermatheca with internal hairs, surface smooth, <J : scutum with bold black and 

 silvery grey pattern or at least with an anterior pair of indefinite subtriangular silvery areas. 

 Genitalia with small tapering or truncate styles much shorter than coxite (Text-fig. 152), style 

 not folded down against body of coxite ; style with one apical spinule (except wellmanni) ; 

 coxite sometimes produced beyond base of style ; ventral plate complex, body usually sub- 

 triangular and toothed apically, basal arms divergent ; median sclerite usually simple and parallel- 

 sided, sometimes bifurcate, end sometimes frayed but not toothed ; parameres long and slender, 

 parameral hooks numerous. Pupa : Gill formed of large thin-walled tubes or of stout primary 

 branches bearing fine secondary filaments, rarely entirely filamentous. Abdomen with normal 

 complement of hooks (except some forms lacking hooks ventrally on segment 5) ; segments 6-9 

 dorsally without spine-combs. Cocoon with well formed neck, shoe-shaped (except albivirgul- 

 atum). Larva : Head and cephalic fans normal. Hypostomium with usual row of nine apical 

 teeth, teeth short and blunt ; 3-10 setae in each hypostomial row, rows divergent behind from 

 lateral margins of hypostomium. Head-spots positive, sometimes indistinct. Postgenal cleft 

 large, much longer than postgenal bridge, usually rounded or bluntly sagittate. Mandible 

 normal, comb-teeth regularly decreasing in size, two serrations. Antenna short, with four seg- 

 ments. Thoracic cuticle bare (one exception). Abdominal shape varied, cuticle with scales or 

 minute spinous hairs. Ventral papillae absent. No accessory sclerites. Rectal scales present. 

 Rectal gills simple or compound. Posterior circlet with 110-220 rows of 18-49 hooks. 



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

 phoretic ; on vegetation and rock-surfaces or stones, mainly in fast waters of rapids 

 and cascades. Female mammalophilic, including anthropophilic. 



Distribution. Widespread throughout the Ethiopian Region, including southern 

 Arabia (Map 9). The subgenus is absent from the Malagasy Region, unless 

 Simulium gyas de Meillon (at present known only from the pupal stage) should later 

 prove to be assignable to Metomphalus. 



Discussion. This large endemic Ethiopian subgenus is very distinctive and has 

 no apparent affinity with any segregate of the Simulium s.l. fauna in either South 

 America or the Oriento-Australasian Regions. It appears to be most closely allied 

 to the Palaearctic (including North African) subgenus Wilhelmia, and Rubzov (1940 : 

 126-127) in his earlier work placed one of the species, 5. medusaeforme Pomeroy, in 

 Wilhelmia. It is now clear that the species of Metomphalus differ considerably and 

 rather consistently from those of Wilhelmia in both sexes and in the larval stage 

 (though not significantly in the pupal stage) and that for a balanced classification 

 within Simulium both groups should be recognized as subgenera. The female of 

 Wilhelmia differs from that of Metomphalus (and in fact from that of all other 

 segregates of Simulium s.l.) in the exceptionally enlarged claws, and the male by the 

 unique and characteristic structure of the genitalia (again unlike that of any other 

 Simulium s.l.) : other differences include most notably the condition of the pleural 

 membrane (always haired in Wilhelmia, almost always bare in Metomphalus) and 

 the vestiture of the larval abdomen (deeply divided trifid hairs in Wilhelmia, scales 

 or simple spinous setae in Metomphalus). The subgenus Metomphalus as here 

 treated corresponds with the medusaeforme-group of Freeman & de Meillon (1953) 

 with 5. damnosum Theobald excluded (see Edwardsellum). 



The immature stages of some species of Metomphalus may occur in slowly-moving 

 water, but those of most forms characteristically occur in fast-moving turbulent 



