58 
From the above lot of puparia collected in the field May 21 
1 separated June 16 all that had not hatched, and placed them 
in a cage with young wheat raised in the insectarium. This 
wheat grew well until late in August, when it was destroyed by 
plant lice, and more was sown. No flies appeared in this cage, 
however, in June, July, or August, as is shown by the notes of 
several observations to that effect, and none appeared until Sep¬ 
tember 20, after which date they were seen September 22, 23, 24, 
25, 27, and 29. A month later (October 20) half-grown larvm 
were found in this cage, and October 22 freshly formed puparia. 
The life of a generation extending through the midsummer period 
was here no less than five months, from May 21. to October 22. 
The reasons for such differences and inconsistencies in the life 
history of the Hessian fly are among the most interesting points 
concerning it still to be determined. 
A trip made by an assistant through some of the western 
wheat-producing counties of our J State during the last week of 
October, 1890, showed a condition in the fields substantially 
parallel to that in our cages. “The summer had been dry, and 
volunteer wheat had begun growing but a very short time be¬ 
fore that sown in September, yet everywhere in these counties 
this wheat was found full to overflowing of larvae and flaxseeds 
of the Hessian fly, the larvae being comparatively few in num¬ 
ber and all nearly ready to form puparia. The sown wheat ol 
the same fields, as compared with the volunteer wheat, was 
nearly free from the fly. There it was chiefly in the larva state, 
from quite small to nearly full growm, only now and then one 
being seen that had formed a puparium. This condition was 
most marked from St. Clair county, in the latitude of. St. Louis, 
to the borders of Morgan county, some seventy miles north. 
From Morgan county to the latitude of Champaign the differ¬ 
ence between the volunteer and sown wheat was not so great, 
and while the former v T as stocked with both larvsc and pupaiia, 
the larvae being relatively more abundant than in the southern 
portion of the territory visited,—the latter had but few 7 larvae, 
they being about full grown and apparently the progeny of the 
same brood of flies that stocked the volunteer wheat. 
Additional data relating to the time of aestivation are afforded 
by some earlier field experiments. 
The summer of 1888 was peculiarly hot and dry in Southern 
Illinois, and the fields of that region were absolutely overrun by 
the chinch bug, and greatly infested also by grasslioppeis. As.a 
consequence repeated search through several counties and general 
inquiry made in Julv and August, 1888, failed to discover a sin¬ 
gle piece of stubble^ in which volunteer wheat was growing^ 
Furthermore, plots of wheat specially sown for expeiimenta 
purposes near Shattuc, in Clinton county, and neai Albion, in 
Edwards county, beginning June 14 and repeated every two 
* From field notes of Mr. .John Marten. 
