DIPTEKA. 



475 



Family PH0RID.4L (Phor'i-dae). 

 The Humpbacked Flies. 



These are minute, dark-colored, usually black flies, which 

 can easily be recognized by their humpbacked form and 

 the peculiar venation of the wings. Certain species are 

 often found running about rapidly on windows, others on 

 fallen leaves. Sometimes they are seen in swarms dancing 

 up and down in the air. 



The head is small ; the thorax large and humped ; and 

 the abdomen rather short. The antennae are apparently 



111,+j in* -5 



Fig. 581.— Wing of Phora. 



one- or two-jointed, the last segment with either a dorsal or 

 a terminal bristle. The coxae are long ; the femora, espe- 

 cially of the hind legs, which are rather long, are widened 

 and flattened. The wings (Fig. 581) are large, and are fur- 

 nished with two strong veins near the costal border, which 

 extend but a short distance beyond the middle of the wing. 

 From these strong veins from three to five weak ones extend 

 across the wing. 



The larvae feed on decaying vegetable matter, dead 

 insects, snails, etc., and some are believed to be parasitic 

 upon other insects. 



