No. 6. DEPARTMENT OF AGRICULTURE. 391 



abundant as to cause much injury, but it is more usually the case 

 that those of the second brood are the ones whose ravages are most 

 seriously felt. The caterpillars of the third brood usually reach 

 the moth stage before winter, but those which fail to develop so 

 far, pass the winter in whatever condition they may happen to be 

 and become adult the following spring. It is possible that in south- 

 ern Pennsylvania a fourth brood may be able to develop, particularly 

 in years when there is a late fall. 



Injuries. 



The first brood of caterpillars does but a moderate amount of dam- 

 age, eating holes in the leaves. When the food available has all 

 been eaten, the caterpillars search for more, starting off together 

 and forming the "armies" which have given to this insect its name. 

 This almost never occurs with the first brood, however, and only 

 ui intervals of several years with the second or third broods, the in- 

 sects not being usually so abundant as to exhaust their food supply. 

 Upon reaching food, the caterpillars begin their work and strip every- 

 thing as they go, and when full grown, either under ground or among 

 leaves and grass, become quite pupae from which the moths sub- 

 sequently emerge. 



Parasites and Treatment. 



The Army worm has a number of parasites which feed upon it 

 and their activity is probably the reason why this insect is not 

 more often a serious pest. Among its most efiicient foes are two 

 kinds of flies which occur in large numbers where the Army worm 

 is abundant. 



Parasites, however, sometimes fail to destroy enough Army 

 worms to prevent much loss, and in such cases, treatment must be 

 resorted to. Where a field is thoroughly infested by these pests, 

 little can be done, but when the caterpillars begin their march for 

 more food, an excellent practice is to plow a furrow across their line 

 of march, throwing the earth towards the advancing army. In order 

 to cross this furrow each caterpillar must crawl over the loose earth 

 thrown up, then cross the bottom, and finally crawl up the steep 

 side. At intervals of a few feet along the bottom of the furrow, holes 

 may be dug (or bored with a post hole auger if the ground will per- 

 mit) and many of the caterpillars will collect in these holes, which 

 may with advantage be made as much as two feet deep. A band of 

 gas tar placed along the bottom of the furrow may be used to hold 

 the caterpillars, w^hen it can be obtained, and sometimes straw scat- 

 tered along in the furrow and set on fire when covered by the cater- 



