FIFTH ANNUAL REPORT STATE ENTOMOLOGIST 



137 



AN ARMY CUTWORM. 



Chorizagrotis anxiliaris. 



On page thirty-nine of the Fourth Annual Report of the State 

 Entomologist the occurrence of an undetermined cutworm is dis- 

 cussed. Specimens of this insect in the larval stage had been sent 

 to this office under date of October 25, 1906, by T. S. Stiles, R. F. 

 D. No. 1, Belgrade, with the statement that they were doing a great 

 deal of damage. Specimens continued to come in from other farm- 

 ers until the very last of November. Larvae were fed in the green- 

 house of the biology department and brought to maturity, and it 

 was found then that they belonged to Chorizagrotis auxiliaris, a spec- 

 ies that has been very abundant and injurious in Colorado, and a 

 very close relative or possibly identical with the army cutworm 

 that became so abundant and very injurious locally in the Bitter 

 Root valley in the spring of 1898. 



The species that ravaged in the Bitter Root valley was deter- 

 mined to be Chorizagrotis agrestis and there seems to be some reason 

 to believe that C. agrestis and C. auxiliaris are one and the same 

 species and identical also with C. introferens. If all are shown to 

 belong to one species it will be clear that our recent outbreak in 

 and around the Gallatin valley is chargeable to the same insect that 

 operated in the Bitter Root valley in 1898, and that facts secured 

 about this insect and this outbreak will but add to the history of 

 that insect. 



It was most fortunate that there was sufficient moisture, after 

 the caterpillars ceased eating and went into the ground, to make 

 it possible to sprout a second seeding and grow a good crop. If 

 there had been an average, or less than average, precipitation, it 

 probably would have been impossible to secure a good crop. Be- 

 low is given the amount of precipitation, in inches, for the months 

 of May, June and July as shown by the records preserved by Prof. 

 Burke of this Experiment Station : 



May June July 



