86 R. W. CROSSKEY 



and bare postnotum of diceros, and apparently some of the larval characters (not 

 seen, and as judged from the larval description given by Marlier, 1950 : 138), differ 

 from those of copleyi, and the assignment to the group is tentative. Marlier's (1950) 

 description under the name S. neavei was due to misidentification, and the name 

 diceros should have been appended by Freeman & de Meillon (1953 : 123) with the 

 suffix ' sp. nov. ' and not ' nom. nov.'. S. diceros on adult characters would run to 

 berneri-grouj) in the foregoing key to species-groups. 



Included taxa. Simulium (Phoretomyia) copleyi Gibbins ; S.(P.) diceros Freeman 

 & de Meillon ; S.(P.) marlieri Grenier ; S.(P.) rickenbachi Germain, Grenier & 

 Mouchet. 



Subgenus XENOSIMULIUM sgen. n. 



Type-species: Simulium imerinae Roubaud, 1905. 



Diagnosis. ^$ : Basal section of radius haired. Pleural membrane bare or haired. Kat- 

 episternum bare. Fore tarsus slender, fore basitarsus 675-8 times as long as its greatest breadth. 

 $ : cibarium unarmed. Tarsal claws with very small or minute pointed basal tooth. Scutum 

 without conspicuous pattern, but with either three very fine longitudinal lines (seen from in front 

 much as in Wilhelmia, Text-fig. 72). or with three broad dark-scaled vittae separated by pale- 

 scaled areas. Abdomen with pale to coppery or blackish scales, evenly distributed or thinner on 

 terminal segments so that these are semi-shining. Seventh sternite sclerotized, moderately well 

 developed. Gonapophyses large and attenuate, pointed apices strongly haired and directed 

 towards each other (Text-fig. 161). Paraprocts enlarged and slightly or distinctly produced 

 downwards. Spermatheca with polygonal surface pattern, without internal hairs. <J : scutum 

 [where known] similar to $. Genitalia with small tapering or slightly truncate styles that are 

 subequal in length to or shorter than coxites ; style with one apical spinule ; coxites not pro- 

 duced beyond base of style ; ventral plate transverse with subparallel basal arms, not toothed ; 

 median sclerite very large and broad, widening and bifurcate apically ; parameres elongate, 

 parameral hooks numerous and varied in size. Pupa : Gill much shorter than pupal body, 

 with 6-19 slightly stiff filaments not noticeably tapering and without sharp black tips. Abdom- 

 inal onchotaxy normal, no supernumerary hooklets and all terminal abdominal segments without 

 spine-combs dorsally. Cocoon with well developed neck. Larva : Head and cephalic fans 

 normal. Hypostomium with usual nine apical teeth, but these very reduced and median and 

 corner teeth hardly at all prominent ; hypostomial setae 7-10 in each row, sides of hypostomium 

 very wide posteriorly and strongly divergent from hypostomial rows. Head-spots positive, 

 sometimes partially concealed in extensive dark pigmentation. Postgenal cleft of medium size, 

 pentagonal, slightly shorter than or subequal in length to postgenal bridge, sometimes narrow 

 lightly sclerotized line extending forwards from cleft to hypostomium. Mandible with excep- 

 tionally large, apically prominent and strongly curved primary brush (Text-fig. 296), first three 

 comb-teeth very large and longer than the unusually small apical teeth ; mandibular serrations 

 usually two, sometimes one supernumerary serration or mandibular margin irregularly jagged. 

 Antenna long and slender, secondarily annulated and appearing to have 6-8 segments. Thor- 

 acic cuticle bare. Abdominal shape normal, in profile gradually widening to last segment then 

 abruptly contracting to circlet. Abdominal cuticle bare. Ventral papillae absent. Accessory 

 sclerites absent. Rectal scales present or (apparently) sometimes absent. Rectal gills simple, 

 without secondary lobules. Posterior circlet with about 180-250 rows of about 24-30 hooks. 



Bionomy. [Oviposition habit unknown.] Larval and pupal stages non-phoretic ; 



