DIP TER A. 
471 
The most distinctive characteristic of the family is the 
presence of a thickening of the membrane of the wing, which 
appears like 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 
band of stippling. Cell III B is closed; and the 2d cell III 
and cell V are large. 
The antennas 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 
