CIRCULAR 3 7 3, U. S. DEPARTMENT OF AGRICULTURE 



containing the copper coils, and the door of the house was closed 

 and made tight. The carbon disulphide was volatilized rapidly by 

 forcing water at a temperature between 140° and 180° F. through 

 the copper coils, and the fan was started to circulate the carbon disul- 

 phide vapor. A period of 15 or 20 minutes was usually sufficient to 

 vaporize the carbon disulphide. After the desired fumigation period 

 had elapsed, the door and window were thrown open to ventilate 

 the room. The treated beetles were then taken to the insectary, where 

 the} 7 were examined at the end of 24 and 48 hours to determine 



the number that 

 were normal, ill, or 

 dead. The same 

 number of untreated 

 beetles was held in 

 the same manner as 

 a check. 



In examining such 

 a large number of 

 insects it was found 

 very difficult to pick 

 out the few that still 

 might be alive, 

 especially since the 

 species involved may 

 feign death when 

 disturbed. This dif- 

 ficulty was solved by 

 placing the beetles in 

 a shallow pan con- 

 taining warm water, 

 whereupon any that 

 ay e r e alive could 

 b e distinguished by 

 movements of 

 their legs or mouth 

 parts. Those that 

 did not move were 

 considered dead. 

 There was no re- 

 c o v e r y of insects 

 after a period of 48 

 hours. It was found 

 that beetles were 

 killed as readily in 

 baskets of fruit as 

 thjey were when exposed directly to the action of the vapor. A sum- 

 mary of the results obtained with various dosages of carbon 

 disulphide is presented in figure 3. 



TEMPERATURE IN FUMIGATION WITH CARBON DISULPHIDE 



Temperature is an important factor in the insecticidal action of 

 carbon disulphide. It was found that a concentration of 5 pounds 

 of carbon disulphide to 1,000 cubic feet for a period of 2 hours killed 

 80 percent of the beetles' at 80° F., 99 percent at 85°, 99 percent at 



Figure 2. — Interior of fumigating chamber at the experi- 

 mental plant : A, Evaporating pan ; B, ventilating fan ; 

 C, hot-water heating pipes ; D, thermotrol ; E, thermo- 

 graph. 



