78 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 9 



difference between the results of other workers and my own apparently 

 is dependent upon the method used. 



Other Benzene Derivatives Giving Similar Results 

 After having obtained results with nitrobenzene, Mr. Marcovitch^ 

 working with me, tried out a number of similar compounds. Paradi- 

 chlorobenzene will kill the fleas on a dog in about two and one half hours. 

 Paradichlorobenzene seems to be less poisonous than nitrobenzene 

 and one cannot obtain as good results in destroying the sheep tick as 

 with nitrobenzene. Ortho, meta, and para cresol were tried but only 

 the ortho cresol was successful. This compound will destroy the 

 fleas in one and one half hours without injury to the animal. Carbolic 

 acid crystals evaporated by heat will produce similar results in one and 

 one half hours, while sahcylic aldehyde, which is ortho hj'droxyl benzal- 

 dehyde, will drive the fleas off the animal in five to ten minutes, but at 

 the end of one and one half hours, the fleas will show signs of life, al- 

 though they die in a few hours. A number of other similar compounds 

 were tried without success. 



The price of the chemicals varies considerably. Under normal con- 

 ditions, nitrobenzene is about 20 cents per lb.; paradichlorobenzene, 25 

 to 30 cents per lb.; carbolic acid, 25 to 30 cents per lb.; salicyhc 

 aldehyde, 70 cents per oz.; ortho cresol, about SI. 00 a pound. 



Conclusion 

 The above experiments open a new field in economic entomology. 

 Considerable work is needed to determine why the poison will destroy 

 an insect without injuring the animal. Experiments on a large scale, 

 such as the fumigation of barns, must be conducted. The chief 

 difficulty in Minnesota is the low temperature of the barns in the winter, 

 which prevents sufficient nitrobenzene being held in the air to produce 

 the desired results. As many entomologists, particularly^ those in 

 the southern states, have better opportunities to study these chemicals 

 under different conditions and on different insects, it is hoped that 

 others will undertake experiments along this line. 



From Division of Economic Zoology, 

 Minnesota Experiment Station, 

 St. Paul, Minn. 



President Glenn W. Herrick: Is there any discussion of this 

 paper? 



Mr. E. p. Felt: I would like to ask if nitrobenzene is explo- 

 sive. 



