FIFTH ANNUAL REPORT STATE ENTOMOLOGIST 141 



be found that were approaching full size, but on April 26 the largest 

 were nearly full grown and measured 50 mm., or about two inches 

 in length. The specimens brought in fairly represented the range 

 of sizes to be found in the field. 



The most advanced specimens went into the earth to pupate 

 very close to May i, and on the 15th all had disappeared. The first 

 pupae were found in the earthen cells on May 6. Around May 15 

 we heard from various quarters that the cutworms were disappearing 

 and that no further damage was being done. However, we wci-e 

 able to find a few caterpillars as late as the first week of July. 



We were unable to secure eggs from the moths that emerged 

 and have no record of when the second brood of cutworms appeared, 

 if there was a second brood. The species certainly was not injuri- 

 ous in the fall of 1907. We believe that for some unaccountable 

 reason the female moths were not able to lay eggs, except in small 

 numbers, and that this explains the disappearance of the insect in the 

 role of a pest. We do not, however, believe that the insect has 

 wholly disappeared. We will probably be able to capture a few 

 specimens next summer. 



We are likewise unable to explain why the species came in such 

 vnusual numbers. The same phenomenon is happening again and 

 again with other pests but the cause has not yet been explained. 



From the records we have secured as here given it is apparent 

 that if there is a second brood of the insect in Montana, as it is be- 

 lieved there is in Colorado, it must pass through all of its trans- 

 formations betwen early in August and not later than the middle of 

 October. That this can occur does not seem probable for the larval 

 stage required at least six weeks and at least nine weeks were spent 

 in the earth preparing to pupate and in the pupal stage. 



Moreover, it will be remembered that by October 25, when Mr. 

 T. S. Stiles sent specimens to the Experiment Station, the brood 

 of caterpillars had reached sufficient numbers and size to attract at- 

 tention. Farmers were much alarmed at this time. It is reasonable 

 to suppose that the caterpillars had been feeding at least ten days, 

 and the eggs were probably laid not much later than October l It 

 is not improbable, therefore, that the moths might have emerged 

 from the pupal stage as early as September at least. It seems, then, 

 more likely that there is but one brood of this insect in Montana. 



