101 



but one found its ravages more apparent upon coming south through 

 the Red River Valley. 



The number of broods of this pest varies of course with the season, 

 depending on whether the season be dry and Avarm or moist and cool; 

 nevertheless that the Hessian fly has normally more than one brood 

 has been for some time such a firm conviction in the mind of the ento- 

 mologist that this season a serious attempt was made to put the mat- 

 ter beyond doubt with gratifying results. It has seemed to the writer 

 that the "flaxseeds" found in stubble in the autumn could hardly 

 account for the immense injury done the crop the ensuing year, unless 

 the fly was more than one-brooded. 



Professor Lugger, our predecessor, always claimed but one brood in 

 this latitude, and none of his reports indicate that he had changed 

 his mind after making this statement. In one of the reports he said : 

 " Not one fly issued from stalks gathered as soon as injurj^ became 

 visible. This assuredly seems to indicate that the flies do not issue 

 during the autumn, as they do farther south, but remain in the culm 

 until the spring." He further found no larvae or puparia in volun- 

 teer wheat growing near fields that had been badly infested. We 

 have found facts this season warranting us to take exceptions to the 

 last two statements. 



The following are in brief the results of this year's work in this 

 direction. Although able to state them briefly, they represent an 

 immense amount of work in examining plants. 



On June 25 larvae of Hessian fly in second stage were brought to the 

 laboratory, and one fly (and it is to be noted, only one), a female, emerged 

 July 19; she lived two days, depositing about 90 eggs on the green 

 blade of wheat. July 1 one larva in first stage, found in field, brought 

 to laboratory, but did not live. On second day larvae in second stage 

 were secured and placed in breeding jar; July 8 they developed pupa- 

 ria, and on August 16 one (and only one), a female, emerged. On 

 October 18 puparia were found on volunteer wheat growing in the 

 stubble after harvest in the northern part of the State. It would 

 seem then that there is normally in Minnesota more than one brood 

 of Hessian fly. "The observations, however, of this season are not to 

 be taken as criteria necessarily for everj^ year. 



Regarding the imagos emerging from puparia which wintered over 

 as the first brood, the breeding experiments above outlined would 

 indicate a second brood of adults July 19, approximately, and a third 

 brood about the middle of August. But what I call the second brood 

 may be supernumerary to the first or to the brood which I call the third. 

 The plants upon which these observations were made were placed in 

 moist sand, thereby seemingly securing favorable conditions for 

 the development of the fly. Volunteer wheat plants growing in 

 stubble or on the plowed land and along edges of fields, which 



