854 AN INTRODUCTION TO ENTOMOLOGY 



The adult flies are found on flowers. In some genera the abdomen 

 is long, with a slender, wasp-like pedicel (Fig. 

 1 1 08) . In others the abdomen is of the more usual 

 form. The larvae are parasitic, chiefly upon 

 bumblebees and wasps, but some species infest 

 locusts. The eggs are deposited by the female, 

 in some cases at least, directly upon the bodies of 

 the bees or wasps during flight. The newly 

 'Pig.iios.—Conops. hatched larvae burrow within the abdominal 

 cavity of their host. 



Nearly one hundred North American species have been described. 



Family CORDYLURID^ 



The Dung-Flies 



The members of this family are often of considerable size for 

 Acalyptratce, they are never very small. The subcostal vein is dis- 

 tinctly separated from vein Ri and ends in the costa ; vein Ri is nearly 

 half as long as the wing, cell M is not minute; the frontal vitta is 

 usually well difi'erentiated from the orbits; and the vibrissse are 

 present. 



Although members of several families of flies frequent excrement 

 certain species of this family and of the Borboridce are so commonly 

 observed about dung and refuse that they have received the common 

 names of dung-flies. Among these are those of the genus Scatophaga; 

 these are rather slender flies, which have the body clothed with 

 yellowish hair, and which are often abundant especially about fresh 

 cow-dung. Other members of this family are foimd in meadows and 

 in moist places; some feed on other insects which they capture. 



The larvae of some species have been bred from excrement ; some 

 live in the stems of plants ; and some are said to be parasitic in cater- 

 pillars. 



This family is named the Scatophagidse by some writers, and by 

 some it is classed with the Calyptratas. 



The family CLUSIIDvE is a small family of rather small flies; only 

 a few representatives of which are found in our fauna. In this family 

 the subcostal vein is distinctly separated from vein Ri and ends in 

 the costa; vein Ri is less than one-third as long as the wing; the so- 

 called front is broad and bristly to or nearly to the base of the an- 

 tenn£e; the frontal vitta is not differentiated from the orbits; the 

 ocellar bristles are usually present; the postvertical bristles are di- 

 vergent; and the vibrissa are present. Larvas of this family have 

 been found in decaying wood and under the bark of trees. 



This family is named the Heteroneuridse by some writers. 



Family HELOMYZID^ 



The members of the Helomyzidaj can be recognized by the follow- 

 ing combination of characters; the wings are armed with a row of 



