339 



Family Chloropidae — The Frit Flies 



Crassiseta species. 



Small to very small, bare or nearly bare flics. 



Head usually rather hemispherical, sometimes more or less tri- 

 angular or rectangular, the face usually nearly vertical or receding; 

 oral vibrissa? weak or absent; front broad, sometimes with bristles, the 

 vertical triangle very large, often extending to the anterior margin of 

 the front. Antennae usually short, with rounded third segment, some- 

 times elongate. Wings of moderate length or rather short, auxiliary 

 vein vestigial; second basal cell united with the discal cell; anal cell 

 absent; fifth vein almost always with a slight, characteristic irregu- 

 larity near the middle of the discal cell. Legs short, the femora rarely 

 greatly thickened. 



These flies are very common and representatives of the family may 

 be collected almost anywhere. The family will be readily recognized 

 as the large vertical or frontal triangle is characteristic and the peculiar 

 gentle curve of the fourth vein is typical of the group. 



The larvag live in grass and other plants and some of them are 

 economic pests of cereals. They are thick and cylindrical, with stout 

 mouth hooks, two segmented antenna and fleshy abdominal ])rotuber- 

 ances for locomotion. 



The generic limits in some cases are evidently weak and it is not 

 always easy to place some species with certainty. I am not certain that 

 the so-called horny geniculate proboscis of Madiza Fallen constitutes a 

 generic character in this case since there is a gradual evolution to the 

 normal type found in Oscinella Becker. The apical section of the pro- 



