THE CODLING MOTH IN MICHIGAN. 85 



Egg deposition commenced in the cages from 3 to 9 days after the 

 emergence of the moths, and most of the eggs were laid within 5 days 

 after egg deposition commenced. In one instance eggs were laid 23 

 days after the emergence of the moth, but as a rule the great majority 

 of the eggs were laid within 8 days of the emergence. 



The number of eggs per female varied considerably in the cages — 

 on an average, 57 eggs per female were obtained. A single female 

 deposited 161 eggs. Under normal conditions in the field the average 

 number of eggs is unquestionably higher and probably approaches 

 80 to 90 eggs per female. 



The average length of life of the moths was found to be 9 days for 

 the males and 11 days for the females. Instances occurred when one 

 male lived 32 days and a female lived 37 days. 



The length of the incubation period of the eggs varied greatly 

 under different temperature conditions. For the first brood the av- 

 erage length was 7 days and for the second brood 8 days. The range 

 of variation extended from 4 to 16 days. 



The effect of the temperature upon the length of the incubation 

 period is shown by a plotted curve in figure 15. 



The length of the feeding period of the larvae of the first brood 

 varied from 17 to 45 days and averaged 25 days for the " transform- 

 ing" larva? and 28 days for the " wintering" larvae. Still larger 

 variation in the length of feeding was observed in the second brood, 

 ranging from 20 to 84 days and averaging 36 days. 



On an average the larvae spun their cocoons and pupated in 7 days. 

 This period varied, however, from 3 to 18 days. 



The pupal stage varied greatly under different temperature con- 

 ditions, as is illustrated in figure 13. The average length of the pupal 

 stage was 18 days and ranged from 1 week to 2 months. 



The length of the first generation, from the time of the appearance 

 of the eggs to the time of emergence of the moths that resulted from 

 the same, averaged 51 days in 1910. During 1911 the duration of the 

 life cycle varied from 29 to 87 days and averaged 50 days. 



The relative abundance of first-brood and second-brood larvae 

 varied from year to year. In 1909 the second-brood larvae surpassed 

 the first brood in numbers and constituted 57 per cent of the larvae 

 for the season. During 1910, owing to the wide-felt scarcity of apples, 

 the second brood only reached one-third the number of the first 

 brood. During 1911 the second brood almost approached the first 

 brood in abundance. 



Of the first-brood larvae only a portion transformed the same 

 season, while the other portion passed the winter in the larval stage. 

 During the three years of observation the ratio between transforming 

 and wintering larvae of the first brood varied from 30: 70 per cent to 



