59 
weeks till the last of July, failed entirely with the exception of 
bhe plot last named, in Edwards county, where light rains in 
August enabled the grain to start. 
Erom the foregoing it follows with practical certainty that no 
Hessian fly bred throughout this whole region in volunteer 
grain previous to the latter half of August, and that whatever 
lies started later must have come from aestivating flaxseeds. 
The earliest to manifest their presence were found in the last of 
bhe experimental plots near Albion, sown July 31. September 
13 larvae were noticed in this plot b}^ the farmer on whose 
ground the experiment was made, and five days later an as¬ 
sistant found there larvae of all ages except very young, and 
puparia just forming, several of them not yet wholly brown. In 
other fieids in that vicinity where volunteer wheat had started, 
larvae were likewise seen, but in none advanced so far as the 
puparium. 
Larvae and flaxseeds from the experimental plot were brought 
bo the office and confined in pots of wheat placed out of 
Joors. October 9 and 10 (1888) the first flies appeared, and 
others at intervals to the the 27th. As six weeks is the short¬ 
est period of a generation of the fly hitherto observed, it may 
reasonably be said that the eggs from which the first flies to 
emerge (October 9) were ha/tched must have been laid as early 
as the last week in August, and can scarcely have been laid 
earlier than the middle of that month, two weeks after the sow¬ 
ing of the plot'* Here the midsummer interval was approxi¬ 
mately two months, counting from the middle of June to the 
middle of August. That these October imagos were in condition 
bo produce a second generation before the beginning of winter 
was shown, not only by the fact of their emergence as imagos, 
but by the further observation that they deposited eggs in our 
breeding cages, and also that pale puparia seemingly recently 
matured were observed there November 12, nearlv two months 
after the transfer of the original specimens from the experi¬ 
mental patch. 
The following experiments were made to determine the length 
of life of the adult. From infested wheat received May 28, 1890, 
and placed on earth in the office, imagos began to emerge the 
2d June. On the 6th June a male which had just appeared 
was isolated to determine its length of life, and two hours later 
four females which had emerged in the interval were similarly 
isolated. On the 7th June one of these was dead and another 
nearly so. On the morning of the 9th all were dead but one, 
and by five o’clock in the afternoon this also had perished. 
* This is the easiest date for the laying of the eggs deduciblo from our observations at 
the office I call attention here, however, to an earlier item from my present field ento¬ 
mologist, Mr. John Marten, published in my Fourth Report (the Fifteenth from the office), 
p. 23, according to which larvae were seen in volunteer wheat during the last few days of 
August. These larvae were well grown but none had formed the puparium. They were 
doubtless at least two weeks from the egg, and the parent imagos were probably on the wing 
no later than the second week in August. 
