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THE CANADIAN ENTOMOLOGIST 



was used at the rate of 1-20. The checks in these experiments 

 gave a death rate of 11.6%. 



Table 2. EfYectiveness of poisons. 



Arranged in order of value according to combined effectiveness 



and rapidity of kiUing. 



Analyzing further these results and especially comparing the 

 value of Paris green with crude arsenous oxid we find that in three 

 experiments where sawdust was used, the Paris green killed 52.7%; 

 in three experiments with sawdust and bran it killed 75%, and in 

 ten experiments where bran alone was used 90%, while the experi- 

 ments with crude arsenous oxid killed, in two experiments where 

 sawdust was used, 41.6%; in three experiments where sawdust 

 and bran was used, 72.2%, and in eight experiments where bran 

 was used 80.2%. Where crude arsenous oxid was used, 1-40, 

 which was the same strength as Paris green, we have a killing 

 power very slightly in favour of Paris green, and it might be stated 

 in this connection that crude arsenous oxid was used even as 

 weak as 1-60 pounds of filler with very satisfactory results, and 

 when used at the rate of 1-25 it was remarkably effective. 



In interpreting these results we must consider not only the 

 ultimate effectiveness of the individual poisons but also the rapidity 

 with which they kill. In analyzing the results from this point of 

 view, we find that Paris green, crude arsenous oxid and sodium 

 arsenite killed with approximately the same degree of rapidity, 

 sodium arsenite being a little more prompt in its action than 

 either of the other two. During the first two days of the experi- 

 ment, calcium arsenate was slower in action but in most cases 



