56 
found almost any time in the summer. From the evidence ^iven by 
Professor Cocker ell the writer is of the opinion that there are only 
two generations of the insect present in Mesilla Park, and that there 
is no sufficient evidence of a third. 
Professor Aldrich in a recent bulletin states that, in his opinion, 
there is at least a partial third brood at Lewiston, Idaho. This con- 
clusion is arrived at as a result of some ver}^ careful 1}^ conducted 
experiments which give evidence, by breeding records, which up to a 
certain point is indisputable. By caging the insects at proper inter- 
vals Professor Aldrich obtained moths of the second generation on 
September 3 and 4. There is no doubt in the mind of the writer that 
these were moths of the second generation. But Professor Aldrich 
failed to state whether or not he obtained eggs from these moths, and 
instead of doing so took unknown field conditions to carry out the 
remainder of his experiments, taking it for granted that the larvae 
entering after September 6 hatched from eggs which had been laid b}^ 
moths of a similar age to those emerging September 3 and 4. As the 
latter were of the A^ery earliest of the second gen::T.tion, there is no 
reason for assuming that the larva? which entered after this time were 
not larvae of the retarded portion of the second generation. B}" using 
the length of the life cycle with the data given it is obvious that these 
larvae belong to the second generation instead of a third. 
CONCLUSION. 
By taking into consideration the evidence which has been derived 
from the band records, from breeding experiments, and observation, 
the writer has no hesitancy in concluding that there are but two gen- 
erations of the codling moth in the arid sections of the West, and that 
it remains to be proven that even a partial third generation of the 
insect is present in an}^ part of the United States. The writer admits, 
however, the possibilit}^ of a partial third generation in the West and 
South, and that careful, accurate work in the future will give us bet- 
ter evidence upon this point and settle the question beyond a doubt. 
By a careful stud}- of the temperatures for several 3'ears in the locali- 
ties where observations have been made upon the number of genera- 
tions of the insect, the writer hoped to be able to give the total 
temperature at which the difierent conditions in regard to the genera- 
tions might occur; but after a great amount of labor this Ayas found 
to be impracticable, principally on account of insufficient accurate 
observations upon the insect, and it was decided to make use of the 
more general life zones in determining the distribution of genera- 
tions. It may be stated that the boundaries between these life zones 
are onh^ approximate; that there are difierent gradations between 
them, and that as jet there are many inaccuracies in the map. Mr. 
Marlatt, from personal experience and the observations of other ento- 
