NATURAL ENEMIES. ' 39 
I had growing at the time under gauze, but otherwise in the open air, ;i small plot 
of badly infested wheat. 21 by 3 feet, in very fortunate condition for the experiment. 
This wheat had been transplanted March 26 from a field near Roodhouse, in Morgan 
County, for use in making observations on the life-history of the Hessian fly, and 
contained when transferred large numbers of the insect in the hibernating pupa- 
rium. Male and female adults had begun to appear in the inclosnre by April 1, and 
these transformations continued to May 13, the greater number of them occurring 
about April 20, when, for a few days, more than twenty adults could lie counted in 
the cage at a time, not to mention others doubtless concealed in the wheat. 
The first lot of foreign parasites was exposed in this cage May 7. and the second 
lot May 11, both packages containing Living adults when opened. 
At the time of the fust introduction eighteen of the wheat stalks were examined, 
and fifteen young larvae of the Hessian fly Mere found upon them, and all the con- 
ditions were thus favorable to the success of the experiment. Four days after the 
introduction of the parasitized foreign material five freshly emerged specimens of 
SemiotcUus nigripes 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 tin 
was overhauled and the puparia were removed and divided into three lots; one to 
be kept at the office for regular observation of the transformations, one to be taken 
into southern Illinois and distributed through fields of stubble containing Hessian 
fly puparia, and a third to be sent, in accordance with your letter of July, to Mr. 
James Fletcher, Dominion 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 parasite insect. Parasites of the new 
generation continued to emerge from the lot kept for observation until Augue 
the exact dates being July 16, 18, 21. 23, 21. 27. 31, and August 1. 6, 10. 12, 10. 20, 23, 2.".. 
and 2!'. 
Most of these were released in a field of moderately infested wheat stubble on the 
experimental farm of the agricultural experiment station at Champaign, begin- 
ning with 4 specimens July 22, and adding 13 on August LIS on August 6,23 on 
August 10, 15 on August 12, and 1 on August 20; 77 adults in all having been thus 
released at this place. 
In the meantime measures had been taken to introduce the parasites on a larger 
scale in southern Illinois, faking with me about two-thirds of the material 
obtained from our breeding-cage experiment — the parasitized puparia still in the 
straws — I traversed several counties from Central ia south to Union County, and thence 
to St. Louis and Jacksonville, stopping at intervals, but finding no satisfactory situa- 
tion until I reached Scott County, July 17. On the farm of Messrs. Edward and 
Frederick Vantyle a held was found 3 miles northeast of Roodhouse, the yield 
of which has been reduced by the Hessian fly from about 30 to ."•"> bushels to the 
aire to 15. It was the only field in the immediate neighborhood which had be 
damaged, and in this one the fly had not been noticed the year before. There was, 
consequently, little probability of excessive native parasitism of the succeeding 
brood, and it seemed likely that the fly would occur there this tall in volunteer 
grain and Later in the regular sowing. 
The owners agreed to leave unplowed a piece of stubble, on which my specimens 
were scattered, while the remainder of the field was to be plowed for wheat within 
a few days. The fact that specimens of the Semiotellua continued to emerge from the 
(heck lot retained at Champaign for some weeks after this distribution is evidence 
that a considerable number of the parasites must ha\ e gone abroad in Scot t County. 
Indeed, forty or fifty of them, which had completed their transformation en route, 
escaped from the box when it was opened in the field. 
It will be seen from the foregoing narrative that we succeeded completely in breed 
ing a generation of the foreign parasite in our plots of wheat infested b\ the lies- 
