300 Journal of Agricultural Research voi. xxii no. e, 



orthogonia larvae as feeding upon fall and spring wheat, oats, barley, flax, 

 beets, onions, cabbages and carrots. 



PERIOD OF INACTIVITY BEFORE PUPATION 



Although Porosagrotis orthogonia larvae are mature and have prac- 

 tically ceased feeding by the middle of June they do not pupate until 

 nearly a month later. During this period they occasionally feed 

 slightly, but for the most part they remain in a semidormant condition, 

 gradually turning whitish in color and shrinking in size just previous 

 to pupation. This was noticed both in the field and under insectary 

 conditions. Notes taken at Wilsall June 20, 1919, state that on that 

 date cutworms were decreasing in numbers and were nearly all full 

 grown. This field was visited again on July 4, when many whitish larvae 

 were found, some of which had formed earthen cells, but no pupae were 

 found in a two-hour search. 



Records kept on 75 larvae in the insectary showed an average period 

 of 20 days of complete inactivity previous to pupation and a period 

 of 26 days in which only very slight feeding took place. 



PUPAI^ PERIOD 



Pupation generally takes place about the middle of July. Out of 

 80 specimens collected as larvae at Wilsall in May, 1919, and reared to 

 adults in the insectary, the average date of pupation was July 19, the 

 earliest date July 2 and the latest August 1 1 . This checked out almost 

 exactly with conditions in the field at Wilsall. 



About a month is spent in the pupal stage. The average length of 

 pupal period of 80 specimens was 29^^ days, the shortest 2 1 days and 

 the longest 40 days. 



The pupae are protected by a cemented earthen cell and are usually 

 found at a depth of 3 to 4 inches in the soil beneath the plants where 

 they last fed. 



SEASONAL ABUNDANCE OF ADULTS 



The earliest emergence of Porosagrotis orthogonia moths which we have 

 on record is July 31, although Gibson {8, p. 30-ji) reports the emergence 

 of a moth of this species on July 19, In general, the period of greatest 

 abundance is during the last two weeks in August and the first week in 

 September. 



The field at Wilsall where Porosagrotis orthogonia larvae destroyed two 

 seedings of wheat during May and June, 19 19, was searched for moths 

 on August 7, but none could be found. A trap light was run until mid- 

 night on this date, and not a moth of this species was taken. On August 

 26 the field was again visited, and numerous moths were found during 

 the day, and at night they came to trap lights by the thousands. The 

 majority of the moths taken at this time were in prime condition and 



