JOURNAL OF AGMCETIMLEESEARI 



Vol. XXII Washington, D. C, NovEm^'^*^?2i No. 6 



PALE WESTERN CUTWORM (POROSAGROTIS 

 ORTHOGONIA MORR.) 



By J. R. Parker, Assistant Entomologist, Montana Agricultural Experiment Station; 

 A. L. Strand, Assistant State Entomologist of Montana; and H. L. Seamans, 

 Special Assistant in Cutworm Investigations, Montana Agricultural Experiment 

 Station ' 



INTRODUCTION 



Extensive injury to grain crops by cutworms was reported from north 

 central Montana during the period from 1915 to 1920. It was at first 

 supposed that well-known species were responsible for the damage and 

 the usual method of control, poisoned bran mash, was recommended. 

 The repeated failure of this method led to a study of the situation, and 

 from the results of numerous rearing records and the personal investiga- 

 tion of many infested fields it was found that the greater part of the losses 

 was caused by the pale western cutworm {Porosagrotis orthogonia Morr.), 

 a species previously not considered of economic importance in Montana. 

 The enormous damage which it has done during the last six years, the 

 rapidity with which it has extended its range, its unusually long period 

 of larval feeding, its comparative freedom from parasites, and the fact 

 that it works underground and can not be controlled by poisoned bran 

 mash, stamp P. orthogonia as the most dangerous of all our western 

 grain cutworms, not excepting even the army cutworm {Chorizagrotis 

 auxiliaris Grote). 



HISTORY OF THE SPECIES 



The species was given its specific name in 1876 by Morrison (15),^ 

 who described it as A gratis orthogonia from specimens collected at 

 Glencoe, Nebr. In 1890 the species was placed under the genus Porosa- 

 grotis by Smith {16, p. 129), who also gave a description of the adult 

 and recorded its occurrence in the following new localities: Colorado, 

 New Mexico, Arizona, and Utah. Dyar {j, p. 139) lists the species and 

 gives its range as the Rocky Mountain region. In 1905 it was reported 



1 The color plate and drawings for this article were done by Miss Helen Lund, with the remarkable 

 accuracy characteristic of her work. Mr. K. M. King, an undergraduate assistant in 1919, conducted the 

 rearing experiments during that year, and many of the observations recorded are based on his very complete 

 insectary notes. 



^ Reference is made by nxunber (italic) to "Literature cited," p. 320-321. 



Journal of Agricultural Research, Vol. XXII, No. 6 



Washington, D. C. Nov. 5, 1921 



aai Key No. Mont.-8 



(289) 



