SIMULIIDAE OF AFRICA 89 



pattern. Genitalia with small truncate styles shorter than coxites, style with one apical spinule ; 

 coxite not produced beyond base of style ; ventral plate transverse or subcordate with short 

 subparallel or slightly divergent basal arms, plate not toothed and with haired apex, usually only 

 slightly curved in profile ; median sclerite rod-like or short and broad with dilated and sometimes 

 cleft apex ; parameres narrow and elongate, parameral hooks very numerous. Pupa : Gill 

 with from 8 to 19 rather short stiff filaments variously branching, filaments of even thickness 

 along their length or only slightly tapering, each filament with sharp pointed blackened tip ; 

 gill much shorter than pupal body. Abdominal onchotaxy normal, no supernumerary hooks 

 and all terminal segments without spine-combs dorsally. Cocoon with well developed neck. 

 Larva : Head and cephalic fans normal. Hypostomium with usual nine apical teeth, teeth 

 short and blunt, median and corner teeth only slightly prominent ; hypostomial setae excep- 

 tionally numerous, 8-29 in each row, when more than about ten or twelve setae present on each 

 side the row is irregularly doubled or tripled and with several of the setae haphazardly clustered, 

 general line of the rows widely diverging posteriorly from lateral margins of hypostomium. 

 Head-spots positive, usually merged into extensive dark pigmentation of head. Postgenal cleft 

 small, shorter than postgenal bridge, in form of subquadrate notch which is often slightly pointed 

 anteromedially or produced so that anterior part of cleft is subtriangular. Mandible normal, 

 comb-teeth large and usually regularly increasing in length from first to third, second comb- 

 tooth sometimes shorter than those on either side, two serrations. Antenna of medium length, 

 subequal to or slightly longer than stem of cephalic fan, pigmented, with four segments. Thor- 

 acic cuticle bare. Abdominal shape normal, gradually expanding to widest at seventh or eighth 

 segment then abruptly contracting to circlet. Abdominal cuticle appearing bare but with 

 sparse minute simple setae (very inconspicuous) posterodorsally. Ventral papillae absent. 

 Accessory sclerites absent or very faint trace present. Rectal scales present or (apparently) 

 sometimes absent. Rectal gills with secondary lobules. Posterior circlet with about 200-250 

 rows of 24-45 hooks. 



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

 phoretic ; torrenticolous, immature stages attached to smooth rock-surfaces, 

 stones, trailing tree-rootlets and other vegetation in very fast cascades, mainly in 

 mountain streams and up to exceptionally high altitudes (known almost to 15,000 

 feet a.s.l.). Female occasionally anthropophilic (habits little known, probably 

 normally ornithophilic but some non-biting forms with atrophied mouthparts 

 occur) . 



Distribution. Confined to, and widespread in, the Ethiopian Region including 

 southern Arabia (Map 7). Apparently absent from most of the Congo Basin and 

 distribution sporadic in West Africa. 



Discussion. This small homogeneous subgenus, especially distinctive in the pupal 

 stage because of the pointed blackened tips to the gill filaments, contains large 

 species (with larvae up to 13 mm. in length) with a striking ecological preference for 

 the fastest cascading waters, often — although by no means invariably — in high 

 mountainous locales. The segregate is especially characteristic of dashing high- 

 altitude streams on the major mountain massifs of eastern Africa such as Mt. Kenya, 

 Mt. Elgon and Ruwenzori, where Anasolen is the dominant (and often the only) 

 subgenus of Simulium occurring above eight or nine thousand feet. Some forms 

 occur at truly montane levels not far below the level of permanent snow ; on 

 Ruwenzori Anasolen species are known to exist up to 13,100 feet and on Mount 

 Kenya up to 14,700 feet, the highest known locality for Simuliidae on the African 



