THE CODLING MOTH IN MICHIGAN. 15 



the end of July. Incubation of the earliest eggs lasted nine days; 

 for eggs laid about June 30, six days; and for later ones laid during 

 the middle and latter part of July, only four to five days. The 

 larvae from the Saugatuck band records (fig. 9) reach a maximum 

 Juh' 31, and inasmuch as the average length of feeding for this brood 

 of larvae was 27 days the date for the maximum hatching would be 

 July 4. On the other hand, on the basis of oviposition and length 

 of incubation the height of the hatching period would be July 6. 



Length of feeding. — Reference has already been made in the pre- 

 vious pages to the fact that a portion of the first-brood larvae do 

 not transform the same year, but winter and complete the life cycle 

 the following year. The transforming and wintering larvae differ 

 in the length of feeding, and the latter are often materially larger 

 in size. Thus on an average the transforming larvae remained in 

 the fruit 25 days against 29 days for the wintering larvae. (See 

 Tables XVI and XVII.) For the entire brood of larvae the shortest 

 feeding period was 17 days, the longest 45 days. 



Tirrn of maturity of larvse,.— -In the field the time of maturity of 

 the larvae is determined from the band-record experiments (fig. 9 

 and Table XXVIII). Thus the period for the first-brood larvae 

 at Douglas, Mich., extended from July 10 to September 10. After 

 the emergence of the moths from the band-record collection it may 

 further be possible to determine the time of maturity of transforming 

 and wintering larvae of this brood. The last transforming larva 

 left the fruit August 8 and the first wintering larvae left the fruit 

 July 20. Tnere is also a difference in the appearance of cocoons 

 whereby the two sets of larvae may be recognized; the transforming 

 larva provides the cocoon with an exit tube, while the wintering 

 larva produces a closed cocoon. (For full description see pp. 6-7.) 



Percentages of transforming and wintering larvse. — From Table 

 XXXI it will be found that 201 larvae of the first brood transformed 

 the same season, while 368 wintered, or 35 per cent transformed 

 and 64.1 per cent wintered. 



Somewhat similar results were obtained from the rearing experi- 

 ments, though these can not be as reliable as the data from the 

 band-record experiments, since the former are from a limited num- 

 ber of observations. Out of a total of 51 larvae, 21 transformed 

 and 30 wintered, or 40 per cent transformed and 60 per cent wintered. 

 (See Table XXII.) 



Larval life in the cocoon. — The length of time required for the 

 making of the cocoon depends largely upon whether the larva is to 

 transform the same season or to winter. A slight individual varia- 

 tion of time naturally does exist for either set of larvae. In case 

 of wintering larvae it is difficult to decide just when the cocoon is 

 completed. The transforming larvae cease to be active from two 

 to three days before pupating. For these, then, the larval life 

 in the cocoon can be readily determined, being considered as the 

 period from the time of leaving the fruit to the time of pupation. 



