SIMULIIDAE OF AFRICA m 



when subtriangular with divergent basal arms, but plate sometimes wider and the basal arms 

 subparallel ; median sclerite large and elongate-ovate or sometimes subcordate or subtriangular 

 or clove-shaped, cleft apically ; parameres large and broad, irregularly subtriangular, tapering 

 towards parameral hooks, the parameral hooks very numerous. Pupa : Gill filamentous, 

 branches elongate and slender (rarely rather dilated basally), filaments branching near base and 

 numbering 6-32 at extremes of range (but filaments only in even numbers 6, 8, 10, 12, 16, 28-32, 

 and most often 6 or 8) ; gill branches directed forwards but whole gill shorter than pupal body. 

 Abdominal onchotaxy normal, segment 2 often with four small spinous supernumerary hairs or 

 hooklets on each side dorsally, and segment 4 often with a small supernumerary hooklet each side 

 ventrally ; spine-comb present dorsally on at least segment 8 and often on other segments from 

 6-9 in addition. Cocoon of varied form, a simple pocket or with neck, well woven, often 

 fenestrate anteriorly or with an open lattice formed of strong loop-like strands and large open 

 spaces, sometimes with large wing-like lateral anterior flaps or with a large anterodorsal flap, 

 always more or less covering pupal body. Larva : Head and cephalic fans normal. Hypo- 

 stomium with usual nine apical teeth, teeth rather blunt and median and corner teeth not very 

 strongly prominent ; 4-15 setae in each hypostomial row, rows lying subparallel to, or only 

 slightly divergent from, lateral margins of hypostomium. Head pigmentation varied, most often 

 with basic negative pattern of pale spots surrounded by darker areas, the pigmentation on 

 cephalic apotome often forming H-shaped mark, sometimes head-spots clearly positive, some- 

 times head with dark infuscation and spots not clearly either positive or negative. Postgenal 

 cleft large, longer than postgenal bridge, mitre-shaped, elongate-subcordate or subtriangular, 

 often with an anteromedian extension that meets the base of the hypostomium so that the post- 

 genal bridge is incomplete medially. Mandible normal, first three comb-teeth evenly decreasing 

 in size, other comb-teeth long and fine ; two mandibular serrations (very rare exceptions have 

 one or two supernumerary serrations). Antenna long or moderately long (normally longer than 

 stem of cephalic fan), with four segments. Thoracic cuticle bare. Abdomen broadest at sixth 

 or seventh segment, well before posterior circlet. Abdominal cuticle bare. Ventral papillae 

 absent (sides of last abdominal segment sometimes slightly swollen like rudimentary sublateral 

 papillae). Accessory sclerites absent. Rectal scales present. Rectal gills with secondary 

 lobules. Posterior circlet with 60-160 rows of 8-25 hooks. 



Distribution. Widely distributed throughout the Nearctic Region (including 

 Alaska and Greenland), the Palaearctic Region (including North Africa, Japan, 

 Sakhalin and the Kurile Islands) and the Oriental Region (including Formosa and 

 the Ryukyu Islands). Absent from the Ethiopian, Malagasy and Australasian 

 Regions. Probably absent from most of the Neotropical Region, but some forms 

 from Central America have been assigned to the subgenus (Dalmat, 1955 ; Vargas 

 & Diaz Najera, 1957) although atypical in several characters. In the Oriental 

 Region distribution extends south-eastwards as far as Malaysia, western Indonesia 

 and Philippine Republic (but not into New Guinea). 



Discussion. In numbers of included species the subgenus Simulium sensu stricto 

 (including the segregate Gnus Rubzov which is here considered to be a synonym) is 

 the second largest subgeneric segregate in the Simulium s.l. fauna of the Holarctic 

 Regions, including about 30 per cent, of the species in both North America and 

 Eurasia ; no recent revision exists for the Oriental Region but Simulium s. str. 

 species probably account for about half the black-fly fauna of that area. The 

 subgenus is usually looked upon, probably justifiably, as including the most 

 ' advanced ' black-flies, or at least the ones retaining the fewest generalized or 

 ' primitive ' characters, and is usually placed last in any sequential classification of 



