101 



l)iit one found its ravaircs more appacciil upon cuiniii^ s(»uih tlM'(»ni:li 

 the Hod nWi'v Valley. 



The nnndx'i" of broods of Ihis jx'st varies of conrsc wiih the season, 

 dependinji' on whether the season be diy and wai-ni or moist and cool; 

 nevertheless that llie Hessian fly has noi'nially more 1 lian one Itrood 

 has been for some timesueh a lii'm conviction in the niiinl of the ento- 

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

 ter beyond doubt witli gi-atifying results. It has seemed to the wi-iter 

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

 account for the immense injury (h^ne tlie crop the ensuing yeai", unless 

 tlie fly was moi-e than one-brooded. 



l*rofessor Lugger, our predecessor, always claimed but one brood in 

 this latitude, and none of his reports indicate tliat 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 injury became 

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

 dui-ing the autumn, as the}- do farther soutli, but remain in the culm 

 until the spring." lie further found no larva* or i)nparia in noIuu- 

 teer wheat gi-owing near fields that had been badly infested. We 

 have found facts this season wai-ranting us to take exceptions to the 

 last two statements. 



The following are in l)rief the results of this year's work in this 

 direction. Although able to state them ])riefly, thej' represent an 

 immense amount of work in examining plants. 



On June :?o larva^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 III; she lived two days, dei)Ositing about lio eggs on the green 

 blade of wheal. Jul}' 1 one larva in first stage, found in field, brought 

 to laboratorj-, but did not live. On second day larvte in second stage 

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

 ria, and on >\ugust 1<> one (and onl}' one), a female, emerged. On 

 October 18 puparia were found on volunteer wheat growing in the 

 stul)ble after liarvest in tiie northei-n i)art of the State. It would 

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

 of Hessian fly. 'I'he observations, however, of tliis season arc uiA to 

 be taken as ciMtei'ia necessarily foi* every year. 



licgarding tlie imagos emerging from puparia which wintcrcMl over 

 as the first brood, tlie breeding experiments above oullim-d would 

 indicate a second l)rood of adults July IK, ai)proxinnit(dy, and a tliird 

 brood about tlie middle of Aiigust. But what I call the second brood 

 may be supernumerai-y to the first or to the brood which I call tin' third. 

 The plants upon which these ol).s<>rvations were made were placed in 

 moist .sand, thei-eby seemingly seeming favorable conditions for 

 the development of the fly. N'cduuteer wheat i>lants growing in 

 stubble or on the plowed land and alon^'- edires of lields. whii-h 



