CUTWORMS AND ARMY-WORMS 289 



has attracted widespread popular interest. In North America 

 periodic outbreaks have been recorded at intervals since 1743. 

 One of the most widespread and injurious broke out in 1861 

 when the caterpillars appeared in greater or less abundance 

 in twenty states. Other notable outbreaks occurred in 1896 

 and in 1914. The insect is always present in low pastures and 

 meadows and nearly every year there are local outbreaks in 

 some parts of the country. Many theories have been offered 

 to account for these widespread and periodic manifestations 

 but no satisfactory explanation has been advanced. Whatever 

 factors are concerned in determining the abundance of this 

 insect in any one year, they must be effective over a wide area. 

 The abundance of the species in different years is undoubtedly 

 dependent on a combination of circumstances, such as temper- 

 ature, drought and moisture, and the prevalence of fungous 

 diseases and parasitic insect enemies. 



The army-worm feeds normally on grasses. When abun- 

 dant it completely destroys its food supply in a given area and 

 then migrates in armies, devouring almost every green thing 

 in its path, although it eats clover only sparingly. Besides 

 grains and grasses, it feeds on bean, sugar-beet, sweet potato, 

 parsley, cucumber, watermelon, celery, pepper, strawberry, 

 cranberry, sugar-cane and many weeds. The caterpillars 

 feed at night or during cloudy weather ; in the heat of the day 

 they hide under any convenient shade. 



In the North hibernation takes place as partly grown cater- 

 pillars, in the South in the larval and adult stages and excep- 

 tionally in the egg stage. The over-wintering caterpillars are 

 rarely sufficiently abundant to attract much notice. In New 

 York these mature in May ; in New Jersey in April. The 

 caterpillar (Fig. 177) is described by Slingerland as follQws : 



When full-grown, army-worms measure nearly 1^ inches 

 in length. They are of a general greenish black color, much 

 lighter on the venter, which is more or less mottled with blackish. 



