134 Journal of Agricultural Research voi. xv.no. 3 



employed was not as compact as is usually the case with the average 

 balled plant. 



Through the kindness of Messrs. J. A. Hyslop, J. J. Davis, and W. O. 

 Ellis, of the Bureau of Entomology, United States Department of Agri- 

 culture, larvae of the wheat wireworm (A'griotcs mancus Say), green June 

 beetle (Cotinus nitida Linnaeus), white grub (Lachnosterna sp.), and 

 Popillia japonica Newman were obtained and fumigated under the fol- 

 lowing conditions: 



All larvae were exposed to the gas in potting soil, previously de- 

 scribed, contained in 3-inch flowerpots, with the exception of those used 

 in experiments 8, 9, and 10 (Table I), in which case 5-inch pots were 

 employed. The position of the larvae varied, being from i to 3 inches 

 from the surface of the soil. 



After the larvae had been placed in the soil, the pots were transferred 

 to the fumigation chamber, the door closed, and the required vacuum 

 produced. At this point the gas was generated and allowed to pass im- 

 mediately to the fumigation chamber. At the completion of the re- 

 quired exposure the gas was removed from the fumigation chamber by 

 drawing a 25-inch vacuum. 



In experiments 2 and 3 the larvae were exposed to the gas for the 

 entire period in a vacuum; in experiment 4 they were exposed to the 

 gas for 30 minutes in a vacuum, and 30 minutes under normal atmos- 

 pheric pressure; and in experiment 5 they were exposed to the gas in a 

 vacuum for 30 minutes, followed by a pressure of 10 pounds for 30 min- 

 utes. With the exceptions noted, all experiments were conducted with 

 a preliminary vacuum of 26 inches for 15 minutes, with exposures under 

 normal atmospheric conditions varying from i>^ to 2 hours. 



CHEMICALS EMPLOYED IN THE GENERATION OF HYDROCYANIC-ACID GAS 



Sodium cyanid guaranteed to contain not less than 5 1 per cent of 

 cyanogen and commercial sulphuric acid (about 1.84 sp. gr., or 66° 

 Baume) were used in all experiments. The cyanid was used in solution 

 prepared by dissolving 4 pounds of sodium cyanid in i gallon of water. 

 The formula employed was as follows : 



Sodium cyanid in solution ounces . . 2% 



Sulphuric acid ounce. . i 



Water ounce. . i 



RESULTS OF THE EXPERIMENTS 



Taken collectively the results given in Table I show that the killing 

 of 100 per cent can not be depended on where the larvae are in balls of 

 earth around the roots of plants, providing a dosage is used which will 

 not injure the stock. Particularly is this true in the case of moist and 

 soaked soil. 



