72 



DECIDUOUS FRUIT INSECTS AND INSECTICIDES. 



which in turn reduced the percentages of transforming larvae as 

 against the percentage of wintering larvae of the same brood (see 

 Table LXXI). The occurrence of an early maximum of larvae in 

 the second-brood larvae was due to the early rate of emergence of the 

 moths of the summer brood, and to favorable climatic conditions. 



During 1910 the codling moths of the spring brood were delayed 

 in the time of emergence of the earliest individuals. The larger 

 number of moths, however, emerged very soon after the first appear- 

 ance of moths, so that for the rest of the season the dates for the 

 occurrence of the separate stages were about normal. The summer 

 moths commenced to appear July 26 and reached a maximum of 



JUME 



5 10 15 20 25 



JULY 



5 10 15 20 25 



AUGU5T 



5 10 15 20 25 



SEPTEMBER 



5 10 15 20 25 



□ETQBER 



5 10 15 20 25 



MDVEMBER 



5 10 15 20 25 



fS/0 



1971 



Fig. 22.— Diagram showing time of leaving the fruit by the first-brood and second-brood larvae of the cod- 

 ling moth during 1909, 1910, and 1911, at Douglas, Mich. (Original.) 



abundance during late August, which has been observed to be the 

 general rate of emergence for the brood. In 1910 the codling 

 moth was naturally limited in numbers as a result of the small 

 crop of apples, and to this must be ascribed the reduced size of the 

 second brood. Of the total number of larvae from the band records, 

 73.2 per cent were of the first brood and only 26.8 per cent of the 

 second brood. In some sections of the Michigan fruit belt the 

 apple crop was so limited that only one brood occurred, the fruit 

 having dropped before the second brood developed. 



The spring of 1911 opened at a normal time. The temperature 

 during the latter part of May and all of June was on an average 

 exceptionally high, and this condition forwarded the development 

 of both plants and insects in a very unusual manner. The moths 

 commenced to emerge at a normal time, as eorrmared with pheno- 



