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differ with species. Assuming this hypothesis to be true we can 
readily determine the date of the appearance of an insect in the 
spring by keeping record of the accumulated temperature and its 
departure from the normal with the aid of the formula worked out 
tor that insect. By considering the degrees of temperature per day 
as heat units the desired date can be readily computed by mathe- 
matical formule; or if the temperatures be platted the determina- 
tion may be made more readily with the aid of a planimeter. 
If this hypothesis be true, we can readily see that a marked excess 
of temperature for a week or two after the daily mean had passed 
68° F., at which time the first weevils would commence to appear, fol- 
lowed by a slight deficiency in temperature subsequently until the 
mean daily temperature had reached 78° F., would result in the date of 
maximum appearance occurring before the norma! rather than after 
it, and vice versa, In a case with the opposite conditions. These con- 
ditions are much more readily appreciable by the study of tem- 
perature platted in curves. | 
That the rainfall is also a factor governing the time of emergence 
is probable, but it will be largely reflected in the temperature. 
Undoubtedly the proper combination of the departure from normal] 
of temperature and rainfall reduced to a formula in which both were 
included in a single “unit of weather” would give us the exact 
method of computation. 
I offer this hypothesis merely tentatively. It may be old for 
aught I know, although I have never seen it apphed to insects. 
However, in fish hatcheries the time of hatching of the eggs is deter- 
dp) 
1904 curve from the normal after passing the point of first emergence (68° F.) is 
at D. One month prior to that would be A” on the normal curve and Z on the 
1904 curve. The normal temperature accumulated between this date and the 
normal date of maximum emergence (where the normal curve crosses TS° F.) at 
B would be the area A’ BC’. Then the date of Maximum emergence in 1904 
would be that date on which temperature had been accumulated equivalent 
to that represented by A’”BC’, which would be determined by an area 
A” ZXY, in which the position of the line XY must be determined by computa- 
tion, with mathematical formule; and upon establishing its position so that 
it confines an area in A” ZNY equal to A’ BC’, the point X will be-the date of 
maximum emergence for 1904, which in 1904 was X’Y’, or May 12. This may 
be readily done by the aid of a planimeter. : 
The curves given are of interest in that prior to the presentation of this 
paper the date of maximum emergence in 1904 had been determined by the 
above method as being between May 9 and 12, according to slight variation 
from above in method of determining. Since then, in January, 1905, the 
author has received Farmers’ Bulletin 211, in which Mr. W. D. Hunter shows, 
on page 21, that the maximum emergence of the weevils in 1904 was on May 
11, which fact was previously unknown to the writer. The close approxima- 
tion seems to lend support to the probability of the hypothesis in general, as 
it has similarly proven correct in at least three other instances. 
