216 F. W. EDWARDS. 



Control Measures.'^ — ^As has been pointed out by several previous writers, the best 

 method for reducing the numbers otSimulium is the cutting and removal of weeds in 

 rivers and streams ; to be effective this should be done in March. This method 

 would not affect those species which live chiefly on stones, such as S. reptans, 

 S. tuberosum and S. latipes. Probably all that could be done to check these species 

 would be the removal of the most heavily infested stones ; the densest colonies could 

 easily be discovered, as they are usually to be found mainly at certain favourable 

 spots. 



Tabulation of Species. 



Adult Males. 



1. Front metatarsi more or less flattened in a vertical plane ; fiont tibiae, and 



usually also the thorax and abdomen, with silvery markings ; claspers 

 flattened dorso-ventrally (Group A) . , . . . . . . ... 2. 



Front metatarsi cylindrical ; front tibiae, thorax and abdomen without 

 silvery markings, though the tibiae may have silvery pubescence ; claspers 

 not flattened (Group B) . . . . . . . . . . . . . . 11. 



2. Hind metatarsi distinctly thickened in a vertical plane ; pubescence of thorax 



somewhat coarser ; claspers three times as long as broad . . . . 3. 



Hind metatarsi slender, nearly cylindrical ; pubescence of thorax very fine ;. 



claspers hardly longer than broad . . . . . . . . . . 10. 



3. Hind tibiae on basal J, metatarsi on basal |, conspicuously pale . . . . 4. 

 Hind tibiae and metatarsi all black, or nearly so . . . . . . . . 6. 



4. Membranous area of pleura with soft hairs ; front metatarsi 5 times as long as 



broad . . . . . . . . . . . . . . ornatum, Mg. 



Membranous area of pleura quite bare (even when freshly emerged) ; front 

 metatarsi about 6J times as long as broad . . . . . . . . 5. 



5. Ciasper rather slender, external margin slightly concave, the spine terminal 



variegatum, Mg. 



Ciasper broader, external margin strongly convex in the middle, the spine 



subterminal . . . . . . . . . . . . monticola, Fried. 



6. Middle tibia i conspicuously yellowish at base . . . . . . . . 7. 



Middle tibiae all black . . 8. 



7. Front metatarsi about 5J times as long as broad ; silvery markings of thorax 



inconspicuous ; stylus of adminiculum hairy . . subornatum, sp. n. 



Front metatarsi about 4 times as long as broad ; two conspicuous rounded 



silvery spots on thorax ; stylus of adminiculum bare . . reptans, L. 



8. Front tibiae conspicuously silvery in front . . . . . . . . . . 9. 



Silvering of front tibiae much less conspicuous ; ciasper rather slender on 



apical half, with a dorsally-projecting thumb-like process near the base 



tuberosum, Ldst. 



* These are well summarised by Wilhelmi in a recent German Government publication 

 (Die Kriebelmiickenplage ; UebersichtuberdieSimuliidenkunde, besondersinpractischen 

 Hinsicht. Jena, Oct. 1920). 



