880 Journal of Agricultural Research vol. vi, no. 23 



and near the surface of the soil in a torpid condition. When taken into 



the hand, they immediately warmed up and began to crawl. There was 



apparently an absence of any quiescence other than torpor induced by 



cold. 



DURATION OF LARVAL FEEDING IN THE SPRING 



In Montana the larvae resume activity with the beginning of the growth 

 of vegetation, which is generally in the latter part of March or early in 

 April. In 1910 the first larvae from the field were sent in on April 24. 

 In 1 91 5 the first to be received at the Experiment Station came on 

 April 2. By April 15 the station was receiving many urgent requests for 

 information regarding control, indicating that the worms were very 

 active. They continued in abundance in the field until about the third 

 week in April and gradually disappeared until early in May, as indicated 

 by many observations in the field and by the correspondence. In 191 5 

 several lots of larvae from various parts of the State were reared in the 

 insectary and began pupating on April 22 and continued until May 19, 

 when the last had transformed. The greater part of these had pupated 

 by May 10. 



In general, the occurrence of the larvae in "armies" may be said to 

 extend from April 1 to May 1. 



PUPATION AND EMERGENCE OF ADULTS 



From the notes of the writer on the rearing and more especially from 

 information regarding the disappearance of the larvae in the field it is 

 clearly evident that by the last week in April in average years the larvae 

 are rapidly disappearing. Pupation takes place in an earthen cell about 

 2 inches under the surface of the soil. The pupa always rests with the 

 anterior end uppermost, and the molted skin lies beside it. 



The duration of the pupal stage, as indicated by the rearing records of 

 many isolated individuals in the insectary and not including rearings 

 conducted during the winter months in an artificially heated greenhouse, 

 varies from 43 to 63 days and averages 54.7 days. From field observa- 

 tions the duration of this stage has been determined to be approximately 

 60 days. The first week in May clearly marks the height of pupation out 

 of doors. On July 16 and 17 fresh moths were found in great abundance 

 in the fields at Willow Creek, while only a very few pupae could be found. 

 It may be safely assumed that the last of the moths were emerging about 

 this date, and the height of emergence was during the first week in July. 



The writer several times has noted that a small advantage of tempera- 

 ture markedly hastens the appearance of the moths of this insect. If 

 kept in a cool place, the emergence of the moths may be greatly delayed. 

 That the time of emergence varies in different seasons is shown by the 

 fact that on July 8, 1910, in attempting to get pupae 8 miles west of Boze- 

 man it was found that the moths had all emerged. This was an early, 

 dry season. It is quite clear that the first of the moths appear in June. 



