METHODS OF EXTERM I \.-lTL\G NOXIOUS ANTS. 575 



ping on it, or, as many writers suggest, the vapor may be exploded 

 at the mouth of the hole with a match, in order to drive the fumes 

 deeper into the chambers. If the latter method is adopted, the hole 

 should be covered with fresh earth immediately after the explosion, in 

 order to put out the fire and confine the fumes. If this is not done, a 

 large portion of the gas will be burned and the efficiency of the treat- 

 ment be lessened thereby. Right at this point an added word of caution 

 must be given. After the explosion the vapor continues to burn with 

 a colorless flame. It is therefore invisible, but its presence may be 

 easily perceived by holding the hand over the opening or by blowing 

 into it. This point should be carefully noted, for if the operator, think- 

 ing the fire had ceased and desiring to make the extermination of the 

 insects doubly certain, should attempt to recharge the hole from a can 

 or bottle, an explosion would surely follow, with possibly fatal results. 

 Explosion does not appear to add to the efficacy of the treatment, and 

 is not at all necessary. If it is not attempted, it may be well to cover 

 the nest with a wet blanket, which will aid greatly in confining the 

 fumes. If any considerable area is infested, as is often the case in 

 lawns, the holes should not be more than one and one-half feet apart 

 each way, and, after the close of the application, the surface treated 

 may be thoroughly watered, as the wet surface will add to the efficiency 

 of the treatment by preventing the rapid diffusion of the fumes into 

 the air." A method recently recommended by Woglum and Wood 

 (Journ. Econ. Entom., 1908, p. 348) would probably prove to be very 

 effective in dealing with the various ants above mentioned. These 

 authors use a solution of potassium cyanide (one ounce of the salt to 

 a gallon of water). Holes are dug and the solution is poured into 

 them in the same way as when bisulphid is used. The ants are killed 

 by the very poisonous cyanide fumes and probably also by getting the 

 liquid into their mouths when they attempt to clean themselves. Kero- 

 sene oil may also be used like the cyanide and bisulphid, but greater 

 quantities are required, as it kills only by contact. 



3. Harvesting Ants.- In the Southwestern States two species of 

 Pogonoiuvnne.v (P. niolefacicns and P. occidentalis) often occupy so 

 much space with their large mounds and cleared areas in the fields, 

 sidewalks and yards, and sting so viciously on the slightest provocation, 

 that it becomes necessary to exterminate their colonies. This is most 

 easily accomplished by means of the bisulphid method described above. 

 Headlee and Dean ( Kans. Exper. Station Bull. No. 154, 1908), how- 

 ever, have recently recommended the following modification of this 

 method, which they found to be very successful in dealing with P. 



