BRITISH FLIES 47 



ciliation which occurs in some species of Sargus, while it becomes an 

 important character in the Dolichopodidce. " Touch hairs " are some very 

 fine hairs which stand out from the normal dwarf bristles beneath the 

 joints of the front tarsi and on the apical portion of the front tibiae in 

 many Tabanidce. and Leptidca and other widely divergent Diptera, and 

 which evidently indicate in some cases affinity, but more likely in other 

 cases only a similarity of habit intended to effect some peculiar purpose ; 

 at one time I thought they were intended to provide blood-sucking species 

 with exceedingly delicate feelers, so that they could alight on a victim 

 without the slightest sense of touch being felt by the latter, and I am still 

 of opinion that they serve this purpose in many cases. 



Sexual ornamentation is very rare in any marked degree in the 

 Beachycera except in the Miceophona, though brighter colours naturally 

 often exist in one sex. The ornamentation of the legs, however, reaches 

 its height in the males of the DulichoiJodidce and in the females of the 

 Empidce, and the males of some Dolichopodidce (Fsilopus, etc.) exhibit 

 some extraordinary sexual characters in the antennae. 



The details of character development might be prolonged to any extent, 

 but scarcely come within the scope of this volume. 



