414 ANNUAL EEPOETS OF DEPARTMENT OF AGEICULTTJRE. 



tine solutions against different classes of insects; field and laboratory 

 studies of the action of various chemicals on scale insects; special 

 investigations of the value of stems of pyrethrum against different 

 classes of insects were made ; exhaustive tests and studies were made 

 of the action of a large number of chemicals on roaches, bedbugs, 

 clothes moths, chicken lice, dog fleas, aphids and red spiders, the re- 

 sults of which will be published. In cooperation with the Bureaus 

 of Entomology and Plant Industry the field tests of the value of 

 dust mixtures were continued and information of much value in con- 

 nection with the enforcement of the act was obtained. The scope 

 of the work has been materially increased this year in order to cover 

 a larger list of fruits and vegetables. In these tests special refer- 

 ence has been made to finely ground sulphur and powdered lead ar- 

 senate diluted with varying proportions of lime and gypsum. These 

 tests have also included considerable work with dry Bordeaux dusts 

 as compared to the liquid homemade mixture. 



Data of value in the enforcement of the insecticide act have been 

 obtained through investigations made in cooperation with the scien- 

 tists of the Bureau of Animal Industry, of certain products known 

 as " Salt-Blocks," which were falsely labeled as tick eradicators, of 

 products sold for use against bots infesting horses, and relative to the 

 use of soda lye as a remedy for and preventive against worms in- 

 festing hogs. 



" A Simple Improvised Apparatus for Hydrogen Sulfide Precipi- 

 tation " has been devised and described in The Journal of Industrial 

 and Engineering Chemistry, volume 9, page 572, August, 1917. 



