INSECTS INJURIOUS TO CORN. 



319 



to allow the adults to emerge. It is quite different, however, with the 

 states north of us, where there seems to be a good reason to believe that the 

 winter is passed not only by the hibernating insects, but by the pupae, 

 and occasionally by the larval stage. It will thus be seen that the army- 

 worm in Missouri has three distinct broods each year, and that the winter 

 is passed by hibernating adults only. 



The army-worm has its ups and downs, but fortunately for the agri- 

 culturists of any given region, it is more often downs than ups. It is a 

 well known fact that the appearance of army-worms in great destructive 

 numbers never has occurred in any given locality for two consecutive 

 seasons. While the army-worm is with us in small numbers every year 

 and can be readily found by a person searching for them in pastures 

 and meadows and wheat fields, yet the insect is held in bounds by a 

 number of foes, some of which will be discussed later on. It appears 

 that it is only about once out of ten times that these natural enemies fail 

 to do their duty, but when they fail, the army-worms succeed in multiply- 

 ing sufficiently to cause the larvae to take upon themselves the habit of 

 marching in great masses, and practically devour every green thing in 

 their path. 



NATURAL ENEMIES. 



While the army- worms are greedily preyed upon by a number of dif- 

 ferent birds, especially the robins and thrushes, and while poultry of all 

 kinds thrive on this luxuriant food, and also while certain parasitic fungi 

 and bacteria also kill numbers of the larvae and pupae, yet the great war 



Fig. 61. — The Red-Tailed Tachina Fly, Winthcmia 4-pustulata, a parasite on the 

 Army-Worm ; a, the fly, natural size ; b, same, much enlarged ; c, army-worm on 

 which the fly has laid eggs, natural size ; d, parasitized army-worms, enlarged. 

 (From Slingerland.) 



