Nov. 5. 1921 Pale Western Cutworm 299 



was known to be badly infested with Porosagrotis orthogonia. It was 

 estimated that about 50 per cent of the total number of cutworms in 

 the soil were on the surface at any one time. They appeared in greatest 

 numbers in the spots where the grain had previously been cut off. At 

 first they merely wandered about over the surface, but later on, as it 

 became dark, they started feeding. Observations were continued until 

 II p. m., at which time the worms were still moving about and feeding 

 upon the leaves of wheat and grass. At 5 a. m. the next morning a 

 few worms still remained on the surface, but all disappeared as the 

 sun came up. The soil around stray wheat plants was noticeably 

 stirred up where the worms had come up and gone down. That this 

 habit of feeding above ground is not a common one is shown by the 

 fact that only in rare instances have we ever found any injury to that 

 part of the grain plant which is above the ground, and in such cases 

 there was always some doubt as to whether the injury might not have 

 been done by some other species. 



LARV^ DO NOT LEAVE FlElvDS AFTER GRAIN IS DESTROYED 



Another unusual habit of Porosagrotis orthogonia is that it seldom 

 migrates even though its food supply becomes exhausted. If, in fol- 

 lowing along the drill row, it fails to find a plant within a few feet, it 

 simply remains where it is, perhaps for several weeks, without feeding 

 or growing to any extent. In fields that are only partially infested the 

 injury shows up as scattered bare spots, and in such places the larvae 

 do concentrate along the edges of the standing grain, but we have never 

 known them to migrate more than a few rods. This habit of remain- 

 ing in the fields where grain has been destroyed has a very important 

 bearing on farm practice, as will be shown by the following example: 

 Eighty acres of winter wheat at Wilsall in 19 19 were completely de- 

 stroyed by May i, the ground being left entirely bare. The field was 

 reseeded to spring wheat the second week in May. On May 24 the 

 grain was just coming through the ground and was being rapidly cut 

 off by cutworms which had remained in the field since the winter wheat 

 had been destroyed, some three weeks before. The worms continued 

 to feed for several weeks and destroyed all the spring wheat. 



The ability to go for a long time without feeding was well shown by 

 a half-grown larva which remained in a rearing can for 12 weeks with- 

 out food and was then fed and reared to maturity. 



FOOD PLANTS 



In Montana this cutworm has been most commonly found feeding 

 upon winter and spring wheat. Oats, barley, rye, flax, and alfalfa 

 have also been attacked. In the insectary, larvae have fed readily and 

 grown rapidly upon dandelion. In Canada, Gibson reports Porosagrotis 



