88 R. W. CROSSKEY 



gill characters cited above, Xenosimulium differs from Freemanellum by having the 

 katepisternum bare, the male styles short, the female abdomen with a moderately 

 well developed seventh sternite, and the pupal gill with more than four filaments ; 

 from Anasolen it differs by the presence of the female seventh sternite, the absence 

 of sharp black tips to the pupal gill filaments, by the longer and much less pigmented 

 larval antenna and by the bare larval abdominal cuticle (in Anasolen larvae there are 

 at least a few minute simple setae posterodorsally on the abdomen) . The characters 

 shared in common with Freemanellum and Anasolen are enumerated in the discussion 

 relating to the latter subgenus. 



In the South American Simulium fauna the group most nearly resembling Mada- 

 gascan Xenosimulium appears to be Grenierella Vargas & Diaz Najera, at least to 

 judge from Wygodzinsky's (1949) excellent figures for the type-species, Simulium 

 (Grenierella) lahillei Paterson & Shannon from Argentina, and from adult and pupal 

 pelt material of lahillei in the British Museum collection ; but the significance of the 

 resemblances is uncertain. Nevertheless, to facilitate comparison of the fauna of 

 the African area with the Neotropical fauna it will be useful to indicate the similarities 

 and differences between Xenosimulium and Grenierella : — 



Shared characters : Basal section of radius haired ; katepisternum bare ; fore tarsus slender ; 

 cibarium unarmed or almost so ; very small female claw-tooth ; similar scutum ; paraprocts 

 produced downwards ; one style spinule ; haired ventral plate with transverse shape and very 

 similar profile ; shoe-shaped cocoon ; stiff pupal gill filaments ; segments 6-9 of pupal abdomen 

 without spine-combs dorsally ; same larval body shape and bare cuticle ; rows of hypostomial 

 setae diverging posteriorly from lateral margins of hypostomium, hypostomial teeth short. 



Differential characters : Female gonapophyses long pointed and directed inwards and male 

 style not longer than coxite in Xenosimulium (gonapophyses not of this shape and male style 

 longer than coxite in Grenierella) ; larval postgenal cleft at most subequal in length to postgenal 

 bridge in Xenosimulium (much longer than postgenal bridge in Grenierella) ; larval antenna long 

 and pale, with secondary annulations in Xenosimulium (short, pigmented, without secondary 

 annulations in Grenierella) ; rectal gills simple in Xenosimulium (compound with very numerous 

 slender secondary lobules in Grenierella) . 



Included taxa. Simulium (Xenosimulium) ambositrae Grenier & Grjebine ; 

 S.(X.) imerinae Roubaud ; S.(X.) iphias de Meillon ; S.(X.) neireti Roubaud. 



Subgenus ANASOLEN Enderlein 



Anasolen Enderlein, 1930 : 94. Type-species : Anasolen adolffriedericianus Enderlein, 1930 

 [=Simulium dentulosum Roubaud, 1915], by original designation. 



Diagnosis. q*$ : Basal section of radius haired. Pleural membrane haired or sometimes bare. 

 Katepisternum bare. Fore tarsus slender or slightly dilated, fore basitarsus 6-8 times as long as 

 its greatest breadth. $ : cibarium unarmed. Tarsal claws with very small or minute tooth, 

 sometimes almost simple. Scutum dull, without definite pattern. Abdomen evenly covered 

 with pale or coppery scales, not shining. Seventh sternite undeveloped or at most trace of 

 rudimentary sclerotization. Gonapophyses small pointed-subtriangular (Text-fig. 158), tips 

 directed slightly towards each other, sometimes slightly curled. Paraprocts normal. Sperma- 

 theca with polygonal surface pattern, without internal hairs, o* : scutum without conspicuous 



