55 
••in to the so-called second autumnal generation are belated fe¬ 
males of the second spring brood. [June 1, 1891. The com- 
flication of this life history is still further increased by the fact, 
ecently demonstrated, of an occasional retardation of meta- 
norphosis such that puparia forming one year will not give the 
ringed fly until eleven or twelve months thereafter. An instance 
>f this sort occurred in the breeding work presently to be re- 
)orted, where a part of a lot of puparia obtained in the field, 
n Mansfield, Scott county, June 21, 1890, lay dormant in our 
nsectarium until the spring of 1891, the winged insects appearing 
ate in April and early in May.] 
The following are the new data on which the foregoing state- 
nents rest: 
From a field of winter wheat near Manchester, Sc-ott county, 
L015 flaxseeds or puparia were collected March 13, 1890, 
wrought to the office and removed from the plants for experi- 
nental use. A plot of ground in the insectarium three feet by two 
eet four inches was enclosed by a rectangular frame three feet 
ligh, covered with suisse and provided with a small door at 
me side. This plot was stocked with winter wheat transplanted 
rom a field on the experimental farm, the plants being first 
carefully searched for possible flaxseeds of the fly. The field 
tself from which this wheat was taken was also watched 
throughout the summer, and its complete freedom from fly at¬ 
tack was thus ascertained. Indeed, as there had been no Hes¬ 
sian fly in this whole region for at least five years, there can 
be no doubt that my small experimental plot was absolutely 
tree from it. 
To this wheat the above mentioned flaxseeds were introduced 
March 25, being so enclosed that they could be readily ex¬ 
amined at any time. March 31 the first winged fly appeared 
a male—and April 2, the next—a female. April 8, there were 
eight or ten in the enclosure; and April 5, the remaining flax¬ 
seeds were divided, a part of them being now placed in a cage 
precisely like the other and similarly situated, except that it 
was provided with young wheat which had been sown under its 
enclosure on the 1st of March. Flies continued to emerge in 
both these cages in gradually increasing number until the 15th 
to 18th of April, after which they became rapidly fewer, the 
last appearing May 1. Our previous observations had given 
us April 9 as the earliest date for the emergence of the imagos 
of this brood, and April 23 as the latest.* In the meantime a 
preliminary examination of the wheat of these plots made May 
9, had shown that they were already fairly well stocked with 
larvae and puparia of the fly, the former ranging from very 
young to full grown, and the latter evidently freshly formed. 
At this time the old flaxseeds of the hibernating generation re¬ 
maining in the cages were removed to avoid all posibility of 
* See Fifteenth Report from this office, p. 33. 
