Diptera 261 



Therevidae. — The Therewda are a rather small family distinguished 

 from the Bombyliidx, to which they are allied, by having five hind- 

 marginal cells on the wings instead of three. The head is broad and 

 bluntly conical, and the three-segmented feelers have always an 

 apical claw; mandibles and blades of first maxills act as piercers. 

 I'he hind-body with seven visible segments is elongate and pointed 

 behind. The legs are very slender, a character which separates these 

 flies from the Asilid^. From the Leptids the claw (instead of a 

 bristle) at the tip of the feelers distinguishes them, as also the 

 presence of two adhesive pads (instead of three) on each foot. The 

 larvse live in fungi and rotting wood. The flies prey upon weaker 

 insects, which they capture by lurking among herbage and suddenly 

 darting out. 



Htnpidae. — The Empidte are a large family of predaceous flies with 

 somewhat slender bodies almost without hairy covering. The head 

 is comparatively small, and the form of the feelers and jaws is like 

 that of the allied families. The hind-body has five to seven visible 

 segments, and the male's claspers or the female's pointed ovipositor 

 are usually conspicuous. The haunches are unusually long in some 

 genera, in others the hind-thighs are very elongate or greatly 

 thickened, or the first tarsal segment very broad. The family is 

 widely distributed. 



Nemestrinidae. — -The NemestriniJa are a family of rather large 

 flies of robust build somewhat like Tabanids or Bombyliids in 

 aspect. From the former they may be known by the unringed 

 terminal segment of the feelers, from the latter by the possession of 

 five hind-marginal cells on the wing. They are widely distributed 

 in tropical Asia and Africa and range northwards into southern 

 Europe. 



Dolichopodidae. — The BolkhopodidiE are a very large family of small, 

 slender flies mostly of bright metallic colours. The third segment of 

 the feelers has in some genera, the bristle at the tip, in others on the 

 upper edge as among the Cyclorrhapha. The members of this family 

 may however be distinguished by the absence of the cross-nervule 

 usually present toward the base of the wing between the two median 

 nervures ; the hinder basal cell thus becomes fused with the discoidal 

 cell. The third longitudinal nervure is not forked, as in the pre- 

 ceding families of Brachycera. The larva; live in damp earth, among 

 trees, or under bark. The flies prey upon weaker insects ; they are 

 very numerous and are often to be found near water, sometimes 

 running over the surface. The family is generally distributed. 



Lonchopteridae. — -The Lonchopterida are a family of small flies 

 characterised by their lance-shaped wings with a sharp angle at the 

 tip. The neuration is not well-developed, as the ulnar nervure 

 is not forked and there are no cross nervules in the middle area 

 of the wing The head is oval with prominent eyes, the thorax, 

 hind-body and legs long. The family is poor in genera and 

 species. 



