286 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 9 



to settle. The weakness of this method lies in the fact that the soil 

 quickly absorbs the liquid and the fumes are liberated so slowly that a 

 small percentage only of the efficiency of the material is realized. 



(3) Fumigation with sulfur fumes. — This process involves the use 

 of a special apparatus for generating the sulfur fumes. The fumes, 

 generated by a fan or bellows, are introduced under pressure into the 

 galleries of the nest. The apparatus is cumbersome and slow to op- 

 erate, much time being lost in building the charcoal fires in the gen- 

 erator. Moreover, the fumes possess only moderate killing power, 

 and, being lighter than air, are with difficulty forced to the utmost 

 parts of the ant-hill. For the same reason, the fumes have a tendency 

 to rise and escape just as soon as the pressure above is released. 



The principle of the method of control, used by the writer, consisted 

 in forcing vaporized carbon bisulfide into the ant-hill. Stated briefly, 

 a jet of air was liberated at the bottom of a volume of carbon bisul- 

 fide contained in a closed vessel, and the air, bubbling up through 

 the liquid, vaporized the bisulfide. The vapor was then forced 

 through a tube out of the generator and down into the galleries of the 

 ants. 



Both laboratory and field tests were conducted, the former to de- 

 termine the actual killing power of the gas and the latter to determine 

 both the killing power and general practicability of the method under 

 field conditions. 



For the laboratory tests, the gas generator consisted of a wide- 

 mouthed bottle with two glass tubes passing through the cork, one of 

 which extended to the bottom of the bottle and the other just through 

 the cork. One hundred cc. of Taylor's Fuma carbon bisulfide was 

 poured into the bottle and air forced through the long tube. The 

 impregnated fumes were conducted through a tube to an open-mouthed 

 bottle into which the ants were placed. A uniform pressure of four 

 pounds to the square inch was maintained and the air-conducting 

 tube was just large enough in diameter to prevent the apparatus from 

 bubbling over. A large series of tests were made, wherein lot.s of four 

 or five ants were placed in the bottle for receiving the charged air and 

 exact record taken of the time required for each ant to stop movement 

 after the gas was introduced. The average was about thirty-three 

 seconds for workers and a little less time for soldiers. If the ants 

 were left in the bottles they did not revive. 



When the generating cells were arranged in series of three, as was 

 anticipated, a little less time was required for kiUing, since the charged 

 air passing from cell No. 1 carried away a part of the bisulfide of No. 2, 

 and a less amount of No. 3, thus indicating that the air after passing 



