INSECTS INJURIOUS TO THE GRAINS AND GRASSES. 79 



The Army-worm [Leucania unipiinda Haworth). 



Almost every year from some portion of this large 

 country reports are received of the ravages of armies of 

 worms sweeping over the grain-fields, like a horde of 

 Vandals. Invariably, also, there has not been a single 

 attack in the infested locality for a number of years, so 

 that the farmer is at a loss to do anything to protect his 

 crops, and by the time information can be received from 

 an entomologist a large portion of them will already have 

 been destroyed. Thus previous knowledge of the habits 

 and remedies for these insects may be of value to him 

 when injury by them is threatened. 



Being a species native to this country, these worms may 

 almost alwa3^s be found east of the Rockies in low, rank 

 growths of grass, which form their habitual breeding- 

 grounds. Yet, though the moth is widely distributed, its 

 chief injuries have been in belts from eastern Iowa to 

 Maine, from northern Texas to northern Alabama, and 

 east of the Blue Ridge Mountains to northern North 

 Carolina. Even in these regions, however, the worms have 

 never been recorded as injurious for two successive years, 

 and the only recent wide-spread outbreaks have bee*n in 

 1861, 1875, 1880, and 1896, though serious injury is 

 almost annually done in restricted localities. Only when 

 their usual feeding-places are exhausted, or when through 

 favorable climatic conditions or the destruction of large 

 numbers of the parasites which hold them in check, they 

 increase in abnormal numbers, do they assume the march- 

 ing habit and mass in armies. 



Life-history. — In the North there are usually three 

 broods each season^ and the insects pass the winter as half- 



