^24 THE DIPTERA 



BRACHYCERA HETERODACTYLA. 



A. Antenna apparently two-jointed with a three-jointed arista. 



Small hunch-backed, quick-running flies — Phoridce. 



B. Antenna always three- jointed. 

 Empodia wanting, vestigial or linear. 



I. Radial 4 and 5 separate. 



[a) Arista dorsal — EmpidcB (in part). 

 [h) Arista terminal. 



(1) Front hollowed out between the eyes. Males 



never holoptic. Proboscis without fleshy 

 labellae at tip — AsilidcB. 



(2) Front plane or convex. Males often 



holoptic. Not more than four posterior 

 cells. Third antennal joint without bristle 

 or style — ScenopinidcB. 



11. Radial 4 and 5 not separate. 



Wings not lanceolate, anal cell short ; second basal cell 

 confluent with distal cell. Not brilliantly coloured 

 — Empidce (in part) . 



The orders Therevidas, Midasidae, and Dolichopodidae, while containing 

 species predatory on other insects, do not appear to attack man. 



Family Asilid^. 



Orthorrhapha hvachyceva with long narrow body, short broad head, prom- 

 inent eyes, third joint of the antennae simple. Thorax narrow in front. 

 Wings with elongate basal cells, third longitudinal vein bifurcate, two inter- 

 calary veins present. Empodium with a horny bristle. 



It is not known whether the Asilidse are really blood-sucking flies or not. 

 It is suspected that they bite in the tropics, but there is no definite informa- 

 tion. 



Family Phorid^c 



Phora femorata occurs occasionally in houses. AphiochcBta ferruginea Brun- 

 ner causes intestinal myiasis. 



Family Scenopinid^. 



Scenopinus fenestvalis Linnaeus is the so-called window fly, which is prob- 

 ably the only household fly which is not injurious to health. 



Family Empid^. 



Orthorrhapha hvachycera with medium or small bodies and small heads. 

 Antennae with the first two joints very small and hardly distinct, the third 

 joint annulated, often with terminal bristle. Wings with three large complete 

 basal cells, of which the third is shorter than the second. The posterior basal 

 transverse vein is parallel to the border of the wing. Empodium membrana- 

 ceous. 



It is doubtful whether these insects attack man. As a rule they live on the 

 juices of other insects and plants. 



