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STATE BOARD OF AGRICULTURE. 



THE ERRATIC ARMY-WORM. 

 (Noctua fennica Tausch.) 



Every season or two, some insect long supposed to be harmless, and 

 usually to be found at almost any time, will become a menace to farmers 

 on aecount of changing its food-plant or by suddenly multiplying to 

 unheard of numbers. The damage at such times may be considerable, 

 but usually the insect quickly relapses to its normal condition and num- 

 bers, being held in check, perhaps, by adverse circumstances, or by 

 parasites, until the proper combination of circumstances occurs again. 

 The erratic army-worm has twice before become injurious under cir- 

 cumstances similar to those of 1897. 



On May 21, a letter was received from Mr. W. S. Carpenter of Menomi- 

 nee, Mich., stating that the army-worms were eating his clover, and as he 

 understood that army-worms did not ordinarily eat clover, he desired 

 an explanation. The specimens sent a few days later were immediately 

 recognized as the young of Noctua fennica. They were velvet-black in 

 color, with a number of longitudinal yellowish lines and a brownish head 

 (Fig. 19b). When full-grown they measure nearly one and one-half inches 



Fig. 19b. Erratic Army-worm {Noctua fennica). 



Fig. 19a. Erratic Army-worm {Noctua fennica): 



in length. These insects did considerable damage in the vicinity of Me- 

 nominee, eating almost everything and even gnawing the bark from young 

 trees. The specimens sent us went into the ground and became pupae on 

 June 10. They should have emerged as moths in a few days, but they 

 all died. The moth is shown in Pig. 19a. While this insect is not known 

 to have the habit of marching in armies, it may be destroyed in the same 

 manner as is the true army-worm. 



