132 



IJSfJumOUS INSECTS 



or spring, usually prevents the worms from origin ating 

 in such meadow or field. Such burning destroys the 

 previous year's stalks and blades, and, as a consequence of 



what we have already stated, the nidi which the female < 



moth prefers. Burning as a preventiye, however, loses j 



much of its practical miportance unless it is pursued ] 



annually, because of the irregularity in the appearance of \ 



the Worm in injurious numbers. Judicious ditching, \ 



i. e., a ditch with the side toward the field to be protected ] 



perpeudicular or sloping under, will protect a field from ' 



invasiou from some other infested region when the worms \ 



are marching. When they are collected in the ditch , 

 they may be destroyed either by covering them with 



earth that is pressed upon them, by burning straw over 3 



them or by pouring a little coal oil in the ditch. A ■■ 



single plow furrow, six or eight inches deep and kept i 



friable by dragging brush in it, has also been known to i 



head them off. \ 



From experiments which we have made we are satisfied • 



that where fence-lumber can be easily obtained it may be ] 



used to advantage as a substitute for the ditch or trench, \ 



by being secured on edge and then smeared with kerosene \ 



or coal tar, the latter being more particularly useful j 



along the upper edge. By means of laths and. a few \ 



nails the boards may be so secured that they will slightly ^ 

 slope away from the field to be protected. Such a 



barrier will prove effectual where the worms are not too ^ 

 persistent or numerous. Where they are excessively 



abundant they will need to be watched and occasionally ' 

 dosed with kerosene to prevent their piling up even with 



the top of the board and thus bridging the barrier. The \ 



lumber is not injured for other purposes subsequently. \ 

 In the invasion of Long Island in 1880, but two methods 



were found successful in checking the march of the Army : 



Worm. Trenches were made by plowing, and in these were i 



distributed freshly cut Eed-top grass, a favorite food with \ 



