259 
_ as determined by the use of 50 degrees F. as the zero of development and 
88, 85, and 87 degrees F. as the degrees of the maximum rate of develop- 
ment of the egg, larva, and pupa respectively; and, second, by using 50 
as the zero of development and 86 as the degree of the maximum rate of 
development for the entire period. The results are recorded in the next 
to the last and the last column, respectively, in the tables. The average 
total for the first generation, as shown in Table 24, computed by the 
latter method, was 1122, or 4 more than the total computed by the former 
method, and for the second generation it was 1119, or 15 more computed 
by the latter method than by the former method. The maximum differ- 
ence amounts to less than half a day in the development period and 
hence the latter method may be used for practical purposes, and the fol- 
lowing discussion will have reference to results obtained by it. 
The average total day-degrees for the female is about 20 greater 
than for the male and 10 greater than the average for the male and the 
female, which indicates that the female has a slightly longer period than 
the male. 
There is a large variation in individuals as to the length of the de- 
velopment period and hence in the total effective day-degrees which ac- 
cumulate during the period. In individual cases these totals varied from 
814 to 1475, but less than 4 per cent. of them were below 950, and less than 
2 per cent above 1350. Since some of the extremely high and extremely 
low totals recorded were probably due to errors in observations, 950 and 
1350 may be regarded as the approximate extremes, 1120 being the 
average. 
The total day-degrees which accumulated during the development 
period of individuals whose larve were reared in picked fruit, as shown 
in Table 25, were 1010, or 109 less tham the average for individuals 
whose larve were reared in apples on the tree, showing that larve de- 
velop more rapidly in picked fruit than in fruit on the tree. 
SEASONAL History oF THE CopLING-MoTH, 1915* 
The seasonal history of the codling-moth was determined at Olney 
by large-cage experiments, supplemented by data secured from band col- 
lections and the life history studies. 
LARGE-CAGE SERIES 
The cages (Fig. 5, 6, 7) used in these experiments were large enough 
to cover entire trees and were used for the purpose of keeping the genera- 
tions under observation separate, so that the number of generations, the 
time of beginning, and the time of ending could be definitely determined. 
The events especially noted were dates when the first and the last moths 
* A preliminary report on the observations and experiments of the year 1915 was_pub- 
lished in the 29th report of the State Hntomologist of Illinois, issued in January, 1916, 
and also in the annual report of the State Horticultural Society for 1915. That panes 
(“On the Life History of the Codling-moth,” by Stephen A. Forbes and Pressley A. Glenn) 
contains some data and discussions not repeated in the present article. 
