29 
tected by trees, until February 28,—the last date on which they 
were found. All attempts at rearing these unprotected larvae 
failed, some dying without forming puparia, while others formed 
puparia that were lighter in color and thinner than the normal 
form/’ 
At the present time (November 26) fields near Albion, in "W liite 
county, are in precisely the condition described above by Mr. 
Marten, about nine tenths of the flies being naked larvae, and 
many of them very small. 
The final fate of these hibernating larvae can only be determined 
by observations next spring.* 
[Imagos of the second brood emerging in our breeding cages 
before harvest, have not ordinarily laid eggs, neither made any 
apparent preparations for that duty, a fact which has suggested 
to me the idea that these midsummer imagos were prepared by 
nature for an interval of waiting before giving origin to another 
generation, this interval corresponding to the period of barren 
stubble fields between harvest and the growth of volunteer gram. 
However, in one instance, imagos which emerged May 24, 1887, 
laid eggs at once in the vials where they were confined, and the 
occurrence of even four broods of the Hessian fly in Illinois be¬ 
comes possible. Confirmation of this supposition is afforded by 
the occasional finding of puparia with living larvm above the upper 
node of the stem as late as July 12, the eggs for which must 
have been laid on the upper leaf of the plant, and consequently 
at a date quite too late for the first or spring generation of ima¬ 
gos. June 80, 1887.] 
SUMMARY AND DISCUSSION. 
From all the foregoing we draw the following important practi¬ 
cal conclusion,—that the development of a third (autumnal ) biood 
of Hessian-fly larvm derived from imagos which emerge after the 
first autumnal frosts, may sometimes make of no effect the piac- 
tice of late sowing—at present the standard defense against the 
fly—or may even make late wheat more subject to injury than the 
earlier plantings. How this comes to pass will be seen when it is 
remembered that late sowing as a defense against the fly is a 
procedure based upon the delicacy of the winged insect and its 
sensibility to frosts. By postponement of wheat seeding until the 
first hard frost of autumn, it is hoped to get beyond the reach ol 
*In our breeding cages these hibernating specimens (Edgewood) gave the ' 
number from April 23 to May 3, 1887, and the proof of a third brood m our| latitude is conbe 
quently complete. 
It must not be forgotten, however, in this connection, that b °th onr own 
those of others show that individuals of each generation may lie dormant in the ^nal 
the whole life of the generation following, finally emerging with the descendants of their ™gmal 
contemporaries. Those puparia which form in May and -June uiay not > _ ‘ e in 
tember, and those which form in volunteer wheat in September may hiber nate a il l emerge 
spring. The division into several broods is consequently not complete, and will probaby 
found less and less so as one passes into more northerly latitudes. 
I suspect that drought may retard the metamorphosis of the larva, and that the generations 
may follow each other more closely and rapidly in wet weather than in dry. 
