464 Journal of Agricultural Research voi. xvm, No. 9 



HABITS AND FOOD PLANTS 



As indicated in the introduction, the fly deposits its eggs on grains and 

 grasses, usually on the very young and tender shoots, but sometimes 

 upon or within the glumes just after heading. In the former case 

 the larva enters the shoot and feeds downward in the middle ; in the latter, 

 it eats out the soft young kernel 



Oviposition was not observed, although eggs were found that had 

 been laid only an hour or two. In one instance, a female was seen to 

 protrude the three terminal segments of her abdomen into a sort of 

 ovipositor (see fig. 6, from an alcoholic specimen) . With this she explored 

 the crevices along the stem formed by overlapping of leaves but finally 

 discontinued the operation without laying. Eggs were found both on the 

 stem close to the ground and on the leaves, the latter, however, always 

 within 3 or 4 inches of the ground. One or two lots were laid in crevices, 

 but most of them were in plain sight. In, about 5 days after the emer- 

 gence of the female her eggs are fully developed and can be seen through 

 the thin side walls of the abdomen. There are normally about 30 of 

 equal size contained in the two ovaries. No indication was seen that 

 other series might develop later, but such may be the case under outdoor 

 conditions. 



During the seasons of 191 5 and 1916, sweepings were made on various 

 grains and grasses, both by the writer and by a number of voluntary 

 assistants,* to ascertain the distribution and preferences of the adult. 

 Usually 200 sweeps with a 12 -inch net were made. An examination of 

 240 lots was made in 1915 and of 310 lots in 1916, in order to sort out the 

 various species of oscinids and related families. In both years Oscinis 

 frilled all others in numbers, with totals of 4,677 and 11,235 out of grand 

 totals of 23,416 and 40,187. 



In the course of this work it soon became manifest that adults of 

 Oscinis frit are rare on grain after it has begun to shoot up to head, or 

 on grasses that are approaching maturity; but they are abundant on 

 wheat and grass that is in an earlier stage, stooling or producing fresh 

 shoots. Bluegrass lawns that are kept sprinkled and mowed yield large 

 records of O. frit practically all through the season. Roadside blue- 

 grass kept grazed yields large numbers before the dry weather of summer, 

 but the records decrease rapidly at this time. Evidently the fly seeks 

 grain or grass that is producing new shoots. They seem to be attracted 

 by an exudation from the fresh epidermis, which they greedily lick, and 

 not by the desire to lay their eggs on the plants. In no case was any appre- 

 ciable number of specimens obtained from sweeping on dicotyledons, 

 unless the stand was noticeably mixed with grass. The maximum 

 record for 1915 was 365 flies in 200 sweeps with a lo-inch net on a blue- 



1 Among these should be mentioned Mr. Norman Criddle, Field Officer for Manitoba of the Dominioa 

 Entomological Branch, C. N. Ainslie, Sioux City, Iowa, and Dr. C. F. Adams, Atherton, Mo. 



