274 APPLIED ENTOMOLOGY 



Control. If Army Worms are discovered before they begin their 

 march, spraying all the plants where they are with a stomach poison 

 is an effective treatment, or if the infested area is small, straw can be 

 spread over it and burned. Once on the march, protection of any crops 

 towards which the caterpillars are marching, either by destroying the 

 insects or by preventing their reaching the crops, is the aim of any treat- 

 ment. Poisoned baits (see under " Cutworms," page 276) may be used for 

 this purpose, or where the ground over which the insects are marching 

 is fairly smooth and firm, the use of a heavy roller is possible. A ditch 

 dug across their line of march or around an infested area is often used, 

 and a log dragged along in the ditch as the caterpillars become thick in it 

 will kill multitudes. Food in a strip ahead of their line of march, sprayed 

 with a stomach poison will result in the poisoning of those which feed 

 there, and in some cases the caterpillars while marching can be reached 

 and killed by a strong contact insecticide. 



The Fall Army Worm (Laphygma frugiperda S. & A.). This insect in 

 many ways resembles the true Army Worm. It has numerous common 

 names such as the "grassworm," " overflow worm," " alfalfa worm," 

 etc., and it is called the Fall Army Worm only in the Middle and Northern 

 States, as it does not appear there before fall. 



FIG. 281. FIG. 282. 



FIG. 281. Moth of Fall Army Worm (Laphygma frugiperda S. and A.), about natural 

 size. (Modified from U. S. D. A. Farm. Bull. 7f-2.) 



FIG. 282. Full-grown Caterpillar of Fall Army Worm, somewhat enlarged. (Modified 

 from U. S. D. A. Farm. Bull. 752.) 



This insect is probably a native of this country. While most destruc- 

 tive in the South it may spread during the season far to the North, 

 reaching the New England States, southern Wisconsin and south- 

 eastern Montana, and extending westward to the Rocky Mountains. 



The moth (Fig. 281) spreads about an inch and a quarter. Its front 

 wings are mottled gray, usually with a light spot near the tip, and the 

 hind wings pearly white, edged with a rather narrow, dark line. It does 

 not seem to be able to live over winter north of the southern parts of the 

 Gulf States. The caterpillar (Fig. 282) feeds upon native grasses pri- 

 marily, but when these are not sufficiently abundant it may attack 

 grains, sorghum, alfalfa, clover, cotton and other crops. 



In what stage this insect spends the winter does not seem to have 

 been positively determined, but it is probably the pupa. The eggs, 



