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JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
beyond guessing that if there is a wide outbreak of Hessian flies im¬ 
pending, we will be able to discove r it, and it will not take us by surprise. 
■ . 
Then, having determined this fact, we further proceed to gather 
enough data—trustworthy data—so that we can say just when the 
people in our state should sow; we determine this by another plan. 
We check several methods against each other. We prepare an emer¬ 
gence cage in which the adult flies can come forth, trying to make the 
conditions in the cage as nearly like those outside as possible. We 
keep a daily record of the number of flies appearing in the cage. We 
also have a certain number of marked wheat plants on which we keep 
the record of the number of eggs that are laid each day, and we scrape 
those eggs off after each examination so as to leave a new, clean slate to 
receive the eggs for the next day. We keep the records throughout the 
egg-laying period, so we have the date of maximum egg-laying. We have 
checking against these two devices, some wire screens set up at right 
angles to each other to catch the wind from all four directions equally 
well, and the wires coated with Tanglefoot; and we take the number of 
flies that are caught daily in that. 
We find these devices check against each other splendidly. There is 
only a difference of a few hours we get as the date of maximum general 
emergence as determined by these three checks against each other, and in 
that way we determine to a considerable extent—in fact, we depend 
quite largely on this combination method to say when the time for our 
wheat growers to sow has come. 
But we do not trust this conclusion absolutely. Suppose we were to 
find from the emergence records, that we were getting several days be¬ 
yond the time which average and long experience, and such records as 
Mr. Larrimer has accumulated, would show to be best. That is one of 
the things that has been right in the back of our heads, as something we 
might be obliged to consider any year. If we were to find the maximum 
emergence crawling up to a very, very late date, the question would come 
up whether we could wait any longer; it might be two or three days 
before we would have the maximum record, but just upon the general 
principle that we would be apt to run into more danger from winter 
killing than from Hessian fly, we would probably give the signal to sow in 
such a case. We have not as yet been compelled to do that, but it has 
been in our minds a number of times that we might be obliged to choose 
this course. 
I recall one or two instances of estimating Hessian fly damage that 
seemed very accurate to us at the time we made the calculations, and yet 
