vii EMPIDAE DOLICHOPIDAE 493 



large hind legs. In Hemcrodromia the front legs are raptorial, 

 the femora being armed with spines on which the tibiae 

 close so as to form a sort of trap. Many Empidae execute 

 aerial 'dances, and some of the species of the genus Hilara, are 

 notorious for carrying veils or nets in the form of silken webs 

 more or less densely woven. This subject is comparatively new, 

 the fact having been discovered by Baron Osten Sac-ken in 

 1S77, 1 and it is not at all clear what purpose these peculiar 

 constructions serve ; it appears probable that they are carried 

 by means of the hind legs, and only by the males. Mik thinks 

 that in H. sartor the veil acts as a sort of parachute, and is of 

 use in carrying on the aerial performance, or enhancing its 

 effect ; while in the case of other species, H. maura and H. inter- 

 stincta, the object appears to be the capture or retention of prey, 

 after the manner of spiders. The source of the silk is not 

 known, and in fact all the details are insufficiently ascertained. 

 The larvae of Empidae are described as cylindrical maggots, with 

 very small head, and imperfect ventral feet ; the stigmata are 

 amphipneustic, the thoracic pair being, however, excessively 

 small ; beneath the posterior pair there is nearly always a tooth- 

 or spine-like prominence present. 



Fam. 27. Dolichopidae. Graceful flies of metallic colours, 

 of moderate or small size, and long legs ; usually with bristles on the 

 fiiorax and legs, the h alter es exposed, squamae 

 being quite absent ; antennae of two short stout 

 joints (of which the second is really two, its 

 t/irision being more or less distinct), ivith a 

 tli read-like or hair-like appendage. Proboscis 

 sltort, fleshy. Claws, pulvilli, and empodium 

 small ; wings with a simple system of nervures, 

 those on the posterior part of the wing are but 

 few, there is no anterior basal cross-vein be- 

 the disced and second basal cells, which 



therefore form but one cell. This is also a \ 23 p 5 u ~ A ;, f ^ 

 very extensive family of flies, of which we i:i>if,i : //>n.<. 



1 i i i i T> -, France. (After 



have probably about 200 species in Britain. p e ms) 



They are conspicuous on account of their 



golden, or golden-green colours, only a few being yellow or black. 



1 Ent. Mag. xiv. 1877, p. 226 ; for a discussion of the subject see Mik, Wien. 

 cnt. Zeit. xiii. 1894, p. 273. 



