54 
ADDITIONAL NOTES ON THE HESSIAN FLY.* 1 
(Cecidomyia destructor , Say.) 
LIFE HISTORY. 
Continued studies of the biography of the Hessian fly directed 
especially to the midsummer period, now enable me to give the 
following’ summary account: 
The hibernating puparia yield the imago from the last of 
March to the first of May, the greater part of the perfect in¬ 
sects of this generation appearing during the first three weeks 
of April. The imagos lay their eggs immediately, and perish 
within three days (apparently without feeding), and the larvae 
hatching from these may reach the puparium as early as May 
9. A part of these puparia may live unchanged throughout 
the summer to emerge in August or September; while from the 
others winged insects may emerge late in May, early in June, 
or, perhaps, even in July. 
That these imagos of a second spring generation lay eggs at 
once we have demonstrated repeatedly, and have also proven 
during the last season, by insectarium work, that they may 
give origin under only fairly favorable circumstances to an 
abundant second spring generation of larvae which, with us, 
formed the puparium late in June, and so passed the summer 
interval. 
This season of aestivation or summer dormancy has lasted 
until August or the fore part of September, when the first 
autumnal flies come forth. These lay their eggs, as they 
emerge, in volunteer or early-sown grain, and consequent 
puparia may appear as early as September 18, a part of them 
to hatch the adult, thus giving origin to a second autumnal 
generation of larvae hibernating in the puparium, and a part 
to continue through the winter, emerging in spring. There may 
be thus two complete generations in a year, and two additional 
partial ones, of which one appears late in spring and the othei 
early in fall. 
I am not yet prepared to say, however, that there must be. 
or even may be, more than three full annual broods of any 
strain, as it still remains-possible that all the flies which give ori- 
* This article is the third of a series on the Hessian fly, the two preceding numbers 
of which have been published respectively in the Fourteenth Report from this office, p. <x>, 
and Fifteenth Report, p. 21. 
