DIPTERA 



3" 



The members of this family have three ocelli; the antennas are three- 

 jointed; the second segment of the antenna? is sometimes vestigial and the 

 third segment bears an arista; the palpi are one-jointed; and the em- 

 podia are not pulvilliform. 



The adults are predacious and hunt for smaller flies and other soft- 

 bodied insects. They are usually found in damp places, covered with 

 rank vegetation. Some species occur chiefly on the leaves of aquatic 

 plants, and about dams and waterfalls; and some are able to run over 

 the surface of water. Others occur in dry places. 



The larva? live in a variety of situations, some in earth or decom- 

 posing vegetable matter, some in the burrows of wood-boring larvae and 

 also under bark; some in the stems of plants; and a few are aquatic. 

 But little is known regarding the habits of the larvae; it is said that 

 some species feed on decaying vegetation, while others are believed to be 

 predacious. 



Fig. 55°. — Wing of Psilopodius sipho. 



Family Empidid^e 



The Dance-flies 



The dance-flies are of medium or small size; they are often seen in 

 swarms flying with an up and down movement under trees or near shrubs 

 and over the surface of water. These flies are predacious, like the 

 robber-flies, but they also frequent flowers. The family is a rather 

 difficult one to characterize owing to great variations in the form of the 

 antennae and in the venation of the wings (Fig. 551). 



Fig. 551. — Wing of Rhamphomyia. 



