DIPTERA. 



471 



The most distinctive characteristic of the family is the 

 presence of a thickening of the membrane of the wing, which 

 appears Hke a longitudinal vein between veins III and V. 

 This is termed the spurious vein, and is lacking in only a few 

 members of the family ; it is represented in Figure 574 by a 



HI, .IIl2-h3 Jll,^, 



V3 + VII I 



Fig. 574. — Wing of Eristalis. 



band of stippling. Cell III^ is closed ; and the 2d cell III 

 and cell V are large. 



The antennae are three-jointed ; the third segment usually 

 bears a dorsal bristle, but sometimes it is furnished with a 

 thickened style. The face is not furnished with longitudinal 

 furrows to receive the antennae as in the Muscidae. The 

 frontal lunule is present, but the frontal suture is wanting. 



The adults frequent flowers and feed upon honey and 

 pollen. Some fly with a loud humming sound like that of 

 a bee ; others hover motionless except as to their wings for 

 a time, and then dart away suddenly for a short distance, 

 and then resume their hovering. 



The larvae vary greatly in form and habits. Some prey 

 upon plant-lice, and are often found in the midst of colonies 

 of these insects ; others feed on decaying vegetable matter, 

 and live in rotten wood, in mud, and in water. Some are 

 found in the nests of ants ; and .some in the nests of bum- 

 blebees and of wasps. 



Among the common representatives of this family there 

 is one that so closely resembles a male honey-bee as to be 



