48 



mon bluegrass {Poa pratensis) , while Doctor Fletcher, in Canada, has 

 reared the flies from maggots in the stems of Agropyron, Deschampsia, 

 Elymus, and Poa, and as he states that the flies are enormously abun- 

 dant in meadows and prairies all the wa}" from northern Quebec 

 through the Lake Superior region, Manitoba, and the Northwest Ter- 

 ritories, there seems to be ample proof of its abilit}^ to sustain itself 

 without trouble among the grasses of that countr3^ 



The extent to which it attacks fall wheat in autumn is entirely 

 obscured from the fact that, in the majority of cases, it is confused 

 in its work of destruction with the Hessian fly. In Ohio, at a time 

 when the Hessian fly was being accused of devastating whole fields of 

 wheat in the fall, by collecting a great number of the affected plants 

 at the beginning of winter and placing them in the insectary 1 reared 

 f uU}^ as man}' of these as I did of the Hessian fl}', which at that time I 

 was especially' engaged in investigating. It is on this account that the 

 entomologist who attempts to stud}' the economics of the Hessian fly, 

 which does not breed in the grasses, will find the greatest difiiculty in 

 weighing the evidence offered by those who can not or will not note 

 the difference in the nature of these insects and the great similarity in 

 the final effects of their attacks upon growing fall wheat in autumn 

 and spring. 



SELECTION OF FOOD PLANTS BY THE ADULTS. 



Either some varieties of the same kind of grain are more or less 

 repugnant to the flies, or else the}' possess a very finely adjusted sense 

 of the larval preferences for certain other varieties, for they certainly 

 exhibit a considerable discrimination in their selection of the difi'erent 

 varieties of wheat on which to place their eggs. Doctor Forbes has called 

 attention to the fact that the most seriously injured fields of wheat in 

 Fulton County, 111., in 1883, were of the Fultz variety. At Lafayette, 

 Ind., June l-t, 1889, among a lot of experiment plats on the experi- 

 ment-station grounds, sown side by side, on the same day, with the 

 same soil and other conditions, there was a marked difference between 

 the number of affected straws in the Velvet Chaff and in the Michigan 

 Amber, the infestation being fully four times greater in the former 

 than in the latter. Even in the case of larger fields bordering each 

 other the conditions did not vary, and where the two varieties over- 

 lapped along the margins the same partiality for the Velvet Chaff had 

 been shown. Doctor Fletcher has also noted a strong prejudice in favor 

 of some varieties of the same kinds of grasses. For instance, while 

 Poa serotina was one of the most seriously affected of all of the grasses, 

 P. pratensis^ P. cs&sia, and P. compressa were almost exempt from 

 attack. Attack on Setaria viridis was observed in a single instance. 



PLACE AND METHOD OF OVIPOSITION. 



According to Forbes, the eggs are placed on the stems of grain, "some 

 being pushed down beneath the ensheathing bases of the leaves and 



