56 



found almost any time in the summer. From the evidence g-iven by 

 Professor Cockerell 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 very carefully conducted 

 experiments W'hich give evidence, by breeding records, which up to a 

 certain point is indisputable. B}^ 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 Held conditions to cany 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 Septemb^er 3 and -i. As the 

 latter were of the very earliest of the second genDration, there is no 

 reason for assuming that the larvte which entered after this time w'ere 

 not larvfe of the retarded portion of the second generation. By using 

 the length of the life cycle with the data given it is obvious that these 

 larva? 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 he proven that even a partial third generation of the 

 insect is present in an}" part of the United States. The writer admits, 

 however, the possibility 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 study of the temperatures for several years 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 different conditions in regard to the genera- 

 tions might occur; but after a great amount of labor this was 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 onW approximate; that there are different gradations between 

 them, and that as yet there are many inaccuracies in the map. Mr. 

 Marlatt, from personal experience and the observations of other ento- 



