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. 



ills 



VIIj+IX 

 FIG. 563. Wing of Thereva. 



The family is a comparatively small one, including but 

 few genera and species. 



Family SCENOPINID^E (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 

 that the body when viewed from the side 

 presents a humpbacked appearance (Fig. FIG ^ FIG ^ 

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

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

 they are very inconspicuous. There are three ocelli. The 

 antennas are three-jointed ; the first and second segments 

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

 bristle (Fig. 567). 

 31 



