ON THE BRITISH SPECIES OF SIMULIUM — ^11. 217 



9. Clasper shaped mucli as in tuberosum, but somewhat broader, and thumb-like 

 process shorter ; adminiculum differing from tuberosum and resembling 

 the following . . . . . . venustum, Say {=austeni, Edw.). 



Clasper much broader, without sub-basal thumb-like process and without 

 articulated spine . . . . morsitans, Edw. 



10. A pair of lateral, almost triangular, silvery markings on front of mesonotum 



argyreatum (Mg.) Ldst. 



These markings greyish, not silvery and continued backwards as two narrow 

 lines to the hind margin of the mesonotum 



argyreatum var. sericatum, Mg. 



11. Venation normal ; second joint of hind tarsi more or less excavated above near 



the base ; legs not densely hairy . . . . . . . . . . . . 12. 



Venation abnormal, an extra vein (^2+3) present; second joint of hind 

 tarsi cylindrical ; legs with long and rather dense hair 



hirtipes, Fries. 



12. Hind metatarsi almost cylindrical, and conspicuously pale towards the base ; 



membranous area of pleura with soft hairs . . equinum (L. ) Edw. 



Hind metatarsi more or less thickened vertically ; entirely dark in colour ; 

 membranous area of pleura quite bare . . . . . . . . . . 13. 



13. Pubescence of thorax golden ; second hind tarsal joint deeply excavated. . 14. 

 Pubescence of thorax dull whitish yellow ; second hind tarsal joint only 



slightly excavated . . . . . . . . subexcisum, Edw. 



14. Hind metatarsi barely three times as long as broad . . . . latipes, Mg. 

 Hind metatarsi quite four times as long as broad . . . . . . . . 15. 



15. Clasper nearly cylindrical, of even widfh throughout . . angustitarsis, Ldst. 

 Clasper much swollen towards the base, and rather short 



aureum, Fries. { = bracteatum, Coq. ; 

 =angustipes, Edw.). 



Adult Females. 



1. Front metatarsi flattened in a vertical plane ; front tibiae, and sometimes 



the thorax, with silvery markings ; last three abdominal tergites shining 

 (Group A) 2. 



Front metatarsi cylindrical ; front tibiae and thorax without silvery markings, 

 though the former may have silvery pubescence ; last three abdominal 

 tergites dull (Group B) 12. 



2. Frons (above antennae) and face (below antennae) grey, dull . . . . 3. 

 Frons blackish, shining (face usually grey) . . . . . . . . . . 5. 



3. Claws with a small sharp tooth just before the middle . . . . . . 4. 



Claws not toothed ; coloration like ornatum ; membranous area of pleura bare 



subornatum, sp. n. 



4 Femora mainly dark ; membranous area of pleura with soft hairs ; front 



metatarsi 5x1 .. .. .. ornatum, Mg. 



Front and middle femora almost all yellow ; membranous area of pleura bare ; 

 front metatarsi 6*5x1 .. .. .. .. variegatum, Mg. 



