The Army worm. 245 



the future mature worms begin to appear. After the second moult occurring 

 3 or 4 days later, or in the third stage, the caterpillars are more distinctly 

 striped, their looping habit is lost, but the front pro-legs are still the smallest, 

 and instead of spinning down when disturbed, the worms curl themselves 

 up. When they reach the fourth stage, 3 or 4 days later, they have many of 

 the characteristics of the mature caterpillars, shown in figure 70, and the 

 pro-legs are of nearly equal size. Two more moults occur at intervals of 3 

 or 4 days before the worms become full-grown. 



This insect thus usually spends from twenty to thirty days of 

 its life as an army-worm or caterpillar. 



Arm}^- worms occur every year in most grass -lands, but 

 their habits of feeding mostly at night, remaining hidden dur- 

 ing the day, and of dropping when disturbed, render them quite 

 difficult to find unless they occur in large numbers ; when young 

 the worms quite closely mimic their food-plants, which also renders 

 their detection less easy. It is said that sometimes one ma}^ pass 

 daily through a grass plot where the worms abound, and never 

 suspect their presence until the plot begins to look bare in patches. 

 Their night-feeding habit reminds one of their near allies in the 

 insect world — the cutworms. But the army-worms do not seem 

 to exhibit the wasteful cutting habit of the cutworms, except 

 when they sometimes cut off the heads of wheat and similar 

 grains; usually only the leaves of the grasses and grains are 

 eaten. 



The fact that the traveling of the worms in large armies is an 

 abnormal habit, cannot be too strongly insisted upon. It is only 

 when so very abundant, and the food of the vicinity in which 

 they were borne is destroyed, that they march in search of further 

 supplies; they are usually from one-half to two-thirds grown 

 when the march begins. 



The rate of travel of the worms when on the march of course 

 varies with the nature of the surface over which they have to 

 crawl. They have been observed to travel at the rate of from 

 one to nearly three feet in a minute, or from four to ten rods per 

 hour. 



The Trayisformations Through the Pupa Stage to the Adult In- 

 sect. — Soon after reaching its full growth, an army-worm ordinarily 

 burrows into the ground for an inch or two and there twists its 



