THE CANKEBWORMS 



15 



ford, which were still feeding, but were apparently full grown and 

 about on the point of leaving the tree. With this one exception, the 

 data in the table agree with observations made in the field. 



Table 6. 



-Entrance into ground of larvae of the fall cankerworm, Wallmgford, 

 Conn., 1919 and 1920. 



In 1919. 



In 1920. 



Date. 



Number 

 of larvae. 



Date. 



Number 

 of larvae. 



Date. 



Number 

 of larvae. 



Date. 



Number 

 of larvae. 



June 1 



June 2 



June 3 



June 4 



June 5 



June 6 



June 7 



2 

 2 

 14 

 26 

 38 

 61 

 14 



June 8 



June 9 



June 10 



June 11 



Total 



1 

 2 

 4 

 1 



June 10 



June 11 



June 12 



June 14 



June 15 



June 16 



June 17 



2 

 13 

 19 

 14 

 19 

 23 

 6 

 1 



June 18 



June 19 



June 20 



June 21 



June 22 



June 23 



Total 



1 

 2 

 2 

 

 1 

 3 



165 



106 



PREPUPAL PERIOD. 



It is impossible to determine by daily examination the exact 

 length of the prepupal period, due to the toughness of the cocoon, 

 which makes it difficult to avoid injuring the larva while opening the 

 cocoon for examination. The approximate period, however, was 

 ascertained as follows : A number of larvae were allowed to enter soil 

 in battery jars and construct their cocoons, which were then sifted out 

 and placed in soil in flowerpots sunk in the ground in the insectary 

 yard. At intervals a number of cocoons were dug up, examined, and 

 the number of larvse and pupse recorded. After having been dis- 

 turbed, and very possibly injured, these individuals were not used for 

 further records, but a fresh lot was used each time. The results of 

 these examinations were as follows : Up to and including the twenty- 

 sixth day none had pupated ; on the twenty-seventh day a few pupse 

 were found; on the thirtieth day half or more of them had trans- 

 formed, and on the thirty-fourth and thirty-fifth days four-fifths 

 of them had pupated. Taking into consideration the possibility 

 that due to disease, parasites, or injury, a certain proportion of the 

 larvse might never have pupated, it seems likely that practically 

 all pupation takes place in 27 to 35 days, with the average prepupal 

 period falling between 31 and 32 days for the normal season. 



EMERGENCE OF MOTHS. 



The moths may begin to emerge at any time in the fall, but do 

 not usually leave the ground in numbers until freezing weather has 

 occurred. In 1919 the lowest temperature previous to the first 

 emergence was 32° F. ; in 1920 the lowest was 37° F. In 1919 the 

 lowest temperature preceding emergence in numbers was 26° F., on 

 November 10, but a much greater emergence followed a minimum 

 temperature of 20° F., on the 16th. In 1920 the first period of 

 emergence in numbers began on November 18, after temperatures 

 of 19° F. on the 13th and 21° F. on the 14th. The maximum emer- 

 gence followed after a minimum temperature of 24° F. on the night 

 of November 29. 



