JOHNAL OF AGRICULTURAL RESEARCH 



DEPARTMENT OF AGRICULTURE 



Vol. VI Washington, D. C, September 4, 1916 No. 23 



OBSERVATIONS ON THE LIFE HISTORY OF THE ARMY L|B|? 



CUTWORM, CHORIZAGROTIS AUXIIJARIS 1 „ ew vow 



By R. A. Cooley, 

 Entomologist, Montana Agricultural Experiment Station 



INTRODUCTION 



The army cutworm (Chorizagrotis auxiliaris Grote) occupies a promi- 

 nent place among the pests of staple crops in the Northwest. Serious 

 outbreaks have occurred at irregular intervals, and more or less damage 

 is done nearly every year. Our knowledge of the life history of the 

 species has been very incomplete, and further facts are obviously needed. 

 The purpose of the present article is to present the results of studies 

 made during several years and particularly some observations made in 

 1 91 5 on the egg-laying habits of the species, together with their bearing 

 on the question of the number of broods in the annual cycle. 



SCIENTIFIC NAME OF THE SPECIES 



In previous years the writer has repeatedly reared to the adult stage 

 larvae which had been taken in destructive colonies of this insect. Among 

 these he has found forms corresponding with descriptions of Choriza- 

 grotis auxiliaris, C. agrestis, and C. introferens. Moths reared from 

 much-rubbed parents caught in the fall of 191 5, as recorded below, 

 when determined were found to include at least two of these forms. 

 Gillette 2 states that he had found these forms occurring together in 

 colonies in Colorado. For these reasons and because C. auxiliaris has 

 priority, this name has been used to designate this insect in the present 

 paper. 



PREVIOUS EXPERIMENTAL EFFORTS 



The attempts of the writer to obtain information regarding the life 

 history of this species, and particularly regarding the egg-laying habits, 

 date back for several years, and a brief summary of these efforts may be 



1 Since completing this manuscript and just as it is about to be offered for publication, the writer 

 received a copy of Strickland's excellent paper, which covers somewhat the same ground. (Strickland, 

 E. H., The army cutworm, Euxoa (Chorizagrotis) auxiliaris Grote. Canada Dept. Agr. Ent. Branch, 

 Bui. 1.3, 1916.) 



2 Gillette, C P. Some of the more important insects of 1903. In Colo. Agr. Exp. Sta. Bui. 94 (Tech. 

 Ser. 6), p. 6. 1904. 



Journal of Agricultural Research, Vol. VI, No. 23 



Dept. of Agriculture, Washington, D. C. Sept. 4, 1916 



is Mont.— 3 



(871) 



