DIPTERA 



313 



SERIES I. CIRCULAR-SEAMED FLIES WITHOUT A FRONTAL SUTURE. 



(Aschiza) 



Family Phorid^: 

 The Humpbacked Flies 



These are minute, dark-colored, usually black flies, which can be 

 easily recognized by their humpbacked form, their peculiar antennae, and 

 the peculiar venation of the wings. Certain species are often found run- 

 ning about rapidly on windows, others on fallen leaves. Sometimes they 

 are seen in swarms dancing up and down in the air. 



The head is small; the thorax large and humped; and the abdomen 

 rather short. The antennae are three- jointed; but the first segment is 

 exceedingly small, and the second is enclosed in the third, so that they 

 appear as single- jointed. The third segment bears an arista. The legs 

 are large and strong and well adapted to jumping. The wings (Fig. 554) 

 are large, and are furnished with a series of strong veins near the costal 

 border, which extend but a short distance beyond the middle of the 

 wing. 



In the females of some species that live in the nests of ants and 

 termites the wings are absent or very much reduced in size. 



The larvae of the different species differ greatly in habits, some feed 

 on decaying vegetable matter, dead insects, snails, etc.; some are com- 

 mon in mushrooms, and are sometimes a pest in mushroom cellars; 

 some are internal parasites of other insects, as bees, wasps, ants, saw- 

 flies, etc. ; several species are known to live in the nests of ants. 



/?:+; R++; 



Fig. 554. — Wing of Phora. 



Family Pipunculid^e 

 The Big-eyed Flies 



The members of this family are small flies with very 



large heads composed almost entirely of eyes (Fig. 555). 



Fio y 555. — Pi- The head is nearly spherical and broader than the thorax. 



The antennas are small, short, three-jointed, with a 



dorsal arista. The ocelli are present. The abdomen is somewhat elongate 



with the sides nearly parallel. The body is thinly clothed with hair or 



