470 Journal of Agricultural Research voi. xviii, No. 9 



pure wild oats. In only 2 lots did any flies emerge. One of these was 

 taken at Manchester Siding, Ind., near Crawfordsville, on July 13 

 and yielded one specimen of O. frit on July 26. The other lot was taken 

 on the edge of Crawfordsville the same day, and on July 26 it was found 

 that two specimens of O. frit had emerged, together with one of O. umbrosa 

 Loew and two of Elachiptera nigriceps Loew, a member of the same 

 family. 



A fair conclusion from the five lines of investigation would seem to be 

 that Oscinis frit, as we have it in this country, does not normally feed 

 upon the oat at all, but that occasional individuals, when compelled, 

 are able to do so. This conclusion, in view of the marked preference 

 for the oat manifested by 0. frit in Europe, appeared to the writer to 

 cast a strong doubt upon the identity of the American species ; but after 

 reviewing once more that phase of the subject he is of the opinion that 

 there is no ground other than a physiological one for asserting that the 

 species in North America is not O. frit. The case appears to resemble 

 those mentioned by Dr. C. Gordon Hewitt (jj) in his presidential 

 address at the 191 6 meeting of the American Association of Economic 

 Entomologists, and others cited in the discussion of the address, in 

 which strains of a species apparently arise which have a special adapta- 

 tion to a certain food plant. 



INFESTATION OF GRASSES 



Much remains to be done in studying the relation of Oscinis frit to 

 grasses. Only a few definite records of infestation exist, although most 

 entomologists who have studied the insect assume that a considerable 

 proportion of the flies, especially in middle and late summer, must breed 

 in them. As already noted, sweepings made by the writer and by other 

 entomologists who sent the material so obtained to him, show that from 

 early summer onward the fly is much more abundant on bluegrass lawns 

 than anywhere else. But sweepings on bluegrass that has begun to 

 head or is in a later stage yield very few specimens, indicating that the 

 presence of young shoots is the attraction. Sweepings on timothy in 

 unmixed stand yield almost no specimens at any time, indicating that 

 it is a plant unattractive to O. frit. 



In 1 91 5 five cages were prepared, each containing growing plants of 

 wheat, bluegrass, and timothy. Several individuals of Oscinis frit of 

 both sexes were placed in each. The only infestation that occurred was 

 in wheat, from a stem of which a single maggot was taken and brought 

 to maturity in a vial. From bluegrass sods placed in two cages no 

 specimens of O. frit emerged, and several examinations of both stems and 

 roots of the same grass gave no indications of infestation. O. frit has, 

 however, been reared from this and other grasses, as the list of food plants 

 will show. 



