860 AN INTRODUCTION TO ENTOMOLOGY 



California. For an account of the structure and habits of this larva 

 see Crawford ('12). 



Family CHLOROPID^ 



This family includes a considerable number of species that are 

 common 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 moder- 

 ately short or very short wings; the subcostal vein is vestigial cells M 

 and I St M2 are not separated by a cross- vein ; the antenna; are usually 

 short and with the third joint rounded ; the vibriss£c are rarely present ; 

 and the postvertical bristles are convergent. 



The larva:' of the different species differ in their habits; many 

 species infest the stems of wheat, oats, rye, clover, and grasses; some 

 live in burrows or cavities in plants made by other insects; a few feed 

 upon the egg-shells and cast-off skins of insects; some live in excre- 

 ment; and species of Caurax develop in the egg-sacs of spiders. 

 Among the more important members of this family is the following 

 species. 



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

 species, measuring from i . i to 2 mm. in length. It was first described 

 by Linnaeus in vSweden, 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 com- 

 mon 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 fr;rm 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. 

 For a detailed account of this species see Aldrich ('20). 



This family is named the Oscinida; by some writers. 



The family ASTEIID^E includes a few genera, mostly exotic, 

 that were formerly classed in the Drosophilidae by some writers and 

 in the Chloropidac (Oscinidae) by others; it can be separated from 

 these families by the characters given in Table B. The best-known 

 representative of the family in our fauna is Sigaloessa Jlaveola, which 

 is widely distributed in the Atlantic states. 



Family DROSOPHILID^ 



The Pomace-flies and their Allies. 



There are certain small yellowish flies from three to four milli- 

 meters in length which are very common about the refuse of cider- 

 mills, decaying fruit, and fermenting vats of grape pomace; these are 

 the pomace-flies (Fig. 1112); their larvae live in the decaying fruit. 



