4 



ures. Clean cultivation, rotation of crops, cleaning up fence corners, 

 close pasturage, the burning over of waste grass land in spring or fall 

 are all preventive measures of great value, since, where these methods 

 are in vogue, the army worm will never be able to get a migratory 

 start, or, in other words, it never becomes so abundant as to necessi- 

 tate migration. 



Bearing in mind the fact that the insect breeds normally in rank 

 grass, such as is usually found along the edges of swamps (not in 

 swamps, for the insect must have comparatively dry earth in which to 

 pupate) or in accidentally overfertilized spots in pasture lands, and 

 that it feeds normally only upon true grasses, the farmer who has 

 once suffered from army-worm attack may easily prevent its recur- 

 rence by winter ])urning or l)y rotation and clean cultivation. 



In cases where the worms have already entered a valuable field of 

 wheat before the farmer has become aware of their presence, and too 

 late to render ditching of any avail, some little good may be accom- 

 plished if the majority of the worms are full grown, or nearly full 

 grown, by the old method of "dragging the rope." Two men, each 

 having hold of the end of a long rope, are sent through the field and 

 the rope is dragged over the heads of the grain. The backward jerk 

 of the stalks jars the caterpillars to the ground, and they are unable to 

 ascend to the heads again for some little time. This is a laborious 

 process, however, and has to be repeated almost immediately. It is 

 only to be undertaken where the numl)er of worms in a field is com- 

 paratively small and where these are, as before stated, full grown or 

 nearly full grown, since in this case they will stop feeding and enter the 

 ground in a day or two. 



NATURAL ENEMIES. 



There is almost no prominent injurious insect in whose economy 

 natviral enemies play a more important part than the army worm. We 

 have said above that in the great majority of cases actual destructive 

 measures against army worms which have once taken full possession 

 of a grass field are hardly necessary. This is because of the fact that 

 generally not more than one worm out of a thousand escapes death 

 from parasitic or predaceous insects. Where the army worm follows 

 its normal habit and feeds only at night, remaining hidden during the 

 day under the surface of the ground at the base of some tuft of rank- 

 growing grass, it is protected from these natural enemies, but when the 

 migratory instinct drives it forth and perverts its normal habit, caus- 

 ing it to march unprotected during the day, the swift-breeding tachina 

 flies attack it at once, multiply most rapidly, and in connection with 

 its other parasites and with the predatory ground-beetles, reduce its 

 numbers once more to the noninjurious point. We have said this is 

 generally the case; there may be exceptions, but we have never seen 

 one. It is important, however, for the farmer to be able to recognize 



