DIPTERA 317 



the head and tail ends together and then suddenly straightening the 

 body; in this way they can leap several inches. 



Family Psilid^e 



The flies of this family are of moderate size and slender. In many of 

 the species the antennas are very long and decumbent, but in others they 

 are of moderate length. The following is our best-known species. 



The carrot rust-fly, Psila yoscb. — The larva of this species infests 

 carrots, celery, parsnips, and parsley. In the case of carrots and parsnips 

 the larva? perforate the roots in all directions; their burrows are of a 

 rusty color, hence the common name of the insect. When celery is at- 

 tacked the fibrous roots are eaten off and destroyed. 



Family Ephydrid^e 



These are small or very small, black or dark-colored flies, that live 

 in wet places. 



Most of the species live about fresh water; but to this family belong 

 the " brine-flies " the larvse of which live in salt or strongly alkaline 

 waters. These are common in pools about salt-works; and in the far 

 West and in Mexico these larvas occur in the alkaline lakes in countless 

 numbers. The best-known " brine-flies " belong to the genus Ephydra. 



Still more remarkable are the habits of the larva of the petroleum-fly, 

 Psildpa petrolei, which lives, feeds, and swims about in the pools of crude 

 petroleum, which are numerous in the various oil-fields of California. 



Family Chloropid^e 



This family includes a considerable number of species that are com- 

 mon in meadows and other places where there is rank growing grass. In 

 such situations they can be collected in large numbers by a sweep-net. 



The members of this family are small bare species; with moderately 

 short or very short wings. - 



The larvae of the different species differ in their habits ; many species 

 infest the stems of wheat, oats, rye, and grasses; some live in burrows in 

 plants made by other insects; some live in excrement, while a few develop 

 in the egg-sacs of spiders. 



Among the more important members of this family is the following 

 species. _ 



The European frit-fly, Oscinis frit. — This is a minute black species, 

 measuring from -^ to -^ of an inch in length. It was first described 

 by Linnaeus in Sweden, where it was a very serious pest of barley, the 

 larvae feeding upon the immature kernels. The light and worthless 

 kernels resulting from this the Swedes called " frits," hence the common 

 name of the species. There are several generations annually. The larvae 

 of the late fall generation winter as stem miners in winter grain; and 

 spring grain is attacked in the same way by the spring generation. In 

 this country the commonest form of injury is to the stems of wheat 

 close to the ground. The larva of this species can be easily distinguished 

 from the larva of the hessian fly by the fact that it works in the center of 

 the stem and crawls actively when removed. 



