180 



than twenty adults could be counted in the cage at a time, not to men- 

 tion others doubtless concealed in the wheat. 



The first lot of foreign parasites was exijosed in this cage May 7, and 

 the second lot May 11, both packages containing living adults when 

 opened. 



At the time of the first introduction eighteen of the wheat stalks were 

 examined, and fifteen young larvse of the Hessian fly were found upon 

 them, and all the conditions were thus favorable to the success of the 

 experiment. Four days after the introduction of the parasitized foreign 

 material five freshly emerged specimens of Semiotellus nignpes were 

 noticed in the cage, and others appeared May 13, June 29 and 30, and 

 July 1, 3, 9, and 14. On the date last mentioned the wheat in the cage 

 was overhauled, and the puparia were removed and divided into three 

 lots; one to be kej)t at the office for regular observation of the trans- 

 formations; one to be taken into southern Illinois and distributed 

 through fields of stubble containing Hessian Fly jniparia, and a third to 

 be sent, in accordance with your letter of July 7, to Mr. James Fletcher, 

 Domiidon Entomologist, Ottawa, Canada. 



The parasitized puparia received from Washington were all spent by 

 this time, or perhaps some time before. Removed from the cage July 

 18, they were kept until October 7 without the appearance of another 

 parasitic insect. Parasites of the new generation continued to emerge 

 from the lot kept for observation until August 29, the exact dates being 

 July 1(3, 18, 21, 23, 24, 27, 31, and August 1, 6, 10, 12, 16, 20, 23, 25, 

 and 29. 



Most of these were released in a field of moderately infested wheat 

 stubble on the experimental farm of the Agricultural Experiment Sta- 

 tion at Champaign, beginning with 4 specimens July 22, and adding 13 

 August 1, 18 August 6, 23 August 10, 15 August 12, and 4 August 20— 

 77 adults in all being thus released at this j)lace. 



In the meantime measures had been taken to introduce the jjarasites 

 on a larger scale in southern Illinois. Taking with me about two-thirds 

 of the material obtained from our breeding-cage experiment — the para- 

 sitized puparia still in the straws — I traversed several counties from 

 Centralia south to Union County, and thence to St. Louis and Jackson- 

 ville, stopping at intervals, but finding no satisfactory situation until I 

 reached Scott County, July 17. On the farm of Messrs. Edward and 

 Frederick Vantyle a field was found three miles northeast of Roodhouse 

 the yield of which had been reduced by the Hessian Fly from about 30 to 

 35 bushels to the acre to 15. It was the only field in the immediate 

 neighborhood which had been so damaged, and in this one the fly had 

 not been noticed the year before. There was consequently little proba- 

 bility of excessive native parasitism of the succeeding brood, and it 

 seemed likely that the fly would occur there this fall in volunteer grain 

 and later in the regular sowing. 



The owners agreed to leave unplowed a piece of stubble on which my 



