62 



in the number of ants in the infested hills, and a decrease of 27 per 

 cent in the number of hills infested by root-lice and of 9 per cent in 

 the number of the root-lice themselves. In another case the number 

 of hills infested by ants was reduced 71 per cent and the number of 

 ants in the infested hills 83 per cent, the number of hills infested by 

 root-lice 86 per cent and the number of root-lice in the infested hills 

 61 per cent. The same experiment showed that deep disking with a 

 20-inch disk was much more effective in diminishing the number of 

 ants and root-lice than was the comparatively shallow disking of a 

 16-inch disk, the difference between the two methods of treatment 

 being 34 per cent and 48 per cent in the number of hills infested by 

 ants and Ijy aphids respectively, and 13 per cent and 35 per cent in the 

 number of these insects themselves. It was incidentally shown b> 

 this experiment that plowing to a depth of four inches does not suf- 

 ficiently break up the nests of the ants, but that about 85 per cent of 

 them may be broken up Ijy plowing six inches deep, the remainder 

 being at least broken into. Pages 48-53. 



9. Observations made at night upon the movements of colonies 

 of ants out of plots treated as above, and across furrows surrounding 

 them, showed nearly two and a half times as many migrations from 

 the ])lots deeply stirred as from the check plot. Migration lines across 

 furrows plowed thru the center of each of the plots a week after 

 planting, showed the amotuit of normal underground movements of 

 the ants at this time. Making due allowance for this, it appears that 

 the migration movement caused by the disturl:)ance of the ants in 

 treated j)lots was more than five times as great as this normal. 



Pages 53-55. 



10. Plowing to a dej^th of six inches in a Galesl)urg field, in 1910. 

 dispersed 55 per cent of the ant colonies in tins field, and one disking 

 aft?r i:)lowing dispersed 15 per cent more. Plowing six inches deep, 

 disking three times, and rolling once, increased the vield of the plot 

 nearly 25 per cent, at a cost of 22 cents a bushel. One 20-inch disk- 

 ing followed hy rolling gave all the advantages obtainable by addi- 

 tional diskings. Pages 55-57. 



11. Fall plowing and one spring disking are much more effective 

 than spring plowing with no disking, the latter containing about three 

 times as many ants and four times as many aphids as the former. 



Pages 57-58. 



12. Change of corn ground to oats for one year, and fall-plowing 

 of the oats stubble, gave a larger yield by 25 per cent than adjacent 

 ground kept continuously in corn, this difference being accompanied 

 by a root-louse infestation of young corn on the oats stubble about 

 one-tenth that found in corn on old corn ground. Pages 58-60. 



