DIPTERA. 465 



earth, fungi, and decaying wood. They feed on decaying 

 animal and vegetable matter and are said to be predaceous 

 also. The pupae are free. 



vnuEfc m 



Fig. 565.— Wing of Thereva. 



The family is a comparatively small one, including but 

 few genera and species. 



Family SCENOPlNlDiE (Scen-o-pin'i-dae). 

 The Window-flies. 



The window-flies are so-called because the best-known 

 species are found almost exclusively on windows ; but the 

 conclusion that these are the most common flies found on 

 windows should not be drawn from this name ; for such is 

 not the case. 



These flies are of medium size, our most common species 

 measuring one-fourth inch in length. They are usually 

 black, and are not clothed with bristles. 

 The thorax is prominent, and the abdomen 

 is flattened and somewhat bent down, so ^=^m± 

 that the body when viewed from the side JF% 

 presents a humpbacked appearance (Fig. Fig s66 Fl ^ s6? 

 566). When at rest, the wings lie parallel, scenopinu*. 



one over the other, on the abdomen ; when in this position 

 they are very inconspicuous. There are three ocelli. The 

 antennae are three-jointed ; the first and second segments 

 are short, the third is long and bears neither a style nor a 

 bristle (Fig. 567). 



