26 F. W. EDWARDS. 



male, though I believe that here again there is a certain amount of individual 

 variation. The female claws also yield important characters, though, like Malloch, 

 I have been unable to discover any differences in the male claws. 



So far as I am aware, no previous writer has noted the well-marked pulvilliform 

 margin of the fourth tarsal joint (see fig. 4, a, etc.) which seems to have been developed 

 instead of true pul villi, of which I have not been able to find any trace. This 

 condition of the fourth tarsal joint is found in both sexes and all species. 



The second hind tarsal joint of nearly all species, as pointed out by Roubaud and 

 figured by Malloch and others, has a distinct dorsal excision near the base (fig. 6, a) . For 

 the species in which this excision is not found (represented in Britain by S. hirtipes, 

 fig. 66) Koubaud proposed the subgenus ProsimuUum, and Malloch has adopted this 

 name in a generic sense. The latter writer has also called attention to the possession 

 of an additional vein in the wings by most species of ProsimuUum {e.g., S. hirtipes, 

 fig. 5, 6). But as intermediates are found with regard to both these characters {e.g., 

 S. meridionale and S. suhexcisum in respect of the tarsi, and S. inutatum and 

 S. pecuarum in respect of the wings), and as other characters {e.g. the female claws) 

 do not support the division, I have considered it inadvisable at present to make 

 any use of the term ProsimuUum, and prefer to regard all the species as constituting 

 a single genus. A more natural division of the genus, at least so far as the British 

 species are concerned, seems to be the one adopted in this paper. 



Fig. 2. Female claws of Simulium, x 325 : 

 a, 8. ornatum ; b, S. argyreatum ; c, 8. latipes ; 

 d, 8. tuberosum ; e, 8. equinum ; f, 8. subexcisum. 



Blood-sucking Habits. 



It woidd appear to be the case that not all the species are addicted to blood-sucking 

 habits, notwithstanding the fact, already alluded to, that the mouth-parts are equally 

 developed in the females of all the species. Our two commonest species, S. ornatum 

 and S. latipes, have never, so far as I am aware, been recorded as biting either man or 

 other animals ; while Dr. A. Lutz, whose admirable work on Brazihan biting flies 

 is well known, made some observations on the habits of S. ornatum in the neighbour- 

 hood of Bath last summer, and formed the opinion that it never does bite. On the 

 other hand, S. reptans and its near allies, and S. equinum, are serious pests in certain 

 districts, but these species, fortunately, are more restricted in their range. More 

 exact knowledge on this subject is a desideratum. 



