Western Army Cutworm 



when they are laid. The young worms feed during the fall until winter 

 comes on. As a rule little or no damage is noticed as a result of this fall 

 feeding. With the coming of cold weather the worms become dormant, 

 in which condition they remain until the coming of warm weather in the 

 spring, when they resume feeding. 



In seasons of normal temperatures the worms feed until about April 

 15th or May 1st. If the season is cold and backward the feeding period 

 is prolonged. Under such conditions the worms have been known to 

 feed until well into May. 



Advantage can be taken of our knowledge of the feeding 

 habits of this worm in the sowing of our crops. In case we have 

 an infested field it can safely be planted to an early maturing crop by 

 waiting until the worms have ceased feeding, which is normally about 

 the middle of April in the latitude of Denver. Farther north, planting 

 should be delayed until about May 1st to 10th. 



The moths begin to appear in numbers about June 15th. From 

 this time until the fore part of July they are most abundant. They 

 often become a nuisance in dwellings, causing much annoyance by 

 flying about the lamps. When very numerous the moths will be found 

 under any object which affords concealment during the day. Old gar- 

 ments hanging on the sides of out-buildings seem to be favorite hiding 

 places. The moths live until fall, when egg laying begins. 



NATURAL ENEMIES 



There are a number of parasitic and predacious insects which prey 

 upon the western army cutworm. The most important of these are: 

 Ichneumon-flies, Braconids, Chalcis-flies and ground beetles and certain 

 species of digger- wasps. Several species of birds destroy great numbers 

 of cutworms also. 



Ichneumon-flies, Braconids and Chalcis-flies sting their eggs into 

 the cutworms, using for this purpose a long slender organ called an 

 ovipositor. This ovipositor is located at or near the tip of the abdomen. 

 After the eggs have been placed in the body of the cutworm the little 

 grubs hatch and immediately begin feeding. These grubs subsist 

 upon the body fluids and fatty substances of the cutworm but do not 

 destroy its vital organs until they are fully grown. 



Ichneumon -fly 



The larva of the Ichneumon-fly 10 (Fig. 5, Plate I, Page 11) does 

 not kill the worm, which changes into a pupa before the parasite's work 

 is finished. The moth never develops in a parasitized pupa, however, 

 for the pupa is killed by the parasite, which gnaws its way out when it 

 is fully developed. Instead of a moth coming forth to lay more eggs to 

 infest our fields, the wasp-like Ichneumon-fly emerges, and if a female 

 it deposits its eggs in other cutworms, thus carrying on the good work 

 of ridding our fields of these pests. 



Braconid 



The larvae of the Braconid 2 (Fig. 6, Plate I, Page 1 1) kill the worm 

 before it changes to a pupa. When fully grown the grubs gnaw their 

 way out of the worm and proceed to spin about themselves little silken 



( 10 - 2 ) See explanation of "'Reference Figures." page 2. 



43 



