METHODS OP REPEESSION. 83 



cover-box for the introduction of the chemicals used m fumigating. 

 Just beneath this opening, which could be closed practically air-tight, 

 was placed the usual earthenware crock for holding sulphuric acid 

 and water. Experunental fumigation of these boxes was commenced 

 with a charge of i ounce of 98 per cent potassium cyanid and the 

 requisite amounts of water and sulphuric acid. This strength was 

 found not to kill any ants hi the box except those which were actually 

 outside the packing at the time of fumigation. Gradually this 

 charge was mcreased untU as much as 4 ounces of cyanid were used 

 at a tinie hi the mclosed space of 22 cubic feet. Even at this strength, 

 which corresponded to 18 ounces of cyanid per 100 cubic feet, ants 

 more than 8 mches from the outside of the box were not affected by a 

 confhiemeiit of four hours. In later experiments an iron rod was 

 used to make holes all through the contents of the box and the same 

 charge used as before, 18 ounces of cyanid per 100 cubic feet. After 

 the gas had been confined for five hours the boxes were exanuned 

 and it was found that only those within a couple of mches of the 

 perforations were killed. Larger charges could not be used, simply 

 because the cover-box would not contain a generator of sufficient 

 capacity. Even had a charge heavy enough for effective results 

 been found its cost would have been prohibitive in practical field 

 work. 



Experiments were accordhigly undertaken with bisulphid of 

 carbon for destruction of the ants hi the boxes. Holes were made to 

 the very bottom of the contents, bisulphid poured hito these, and 

 the metal cover placed over the box, its lower edges afterwards 

 being mounded up with dirt. One-half pound of bisulphid, used in 

 this inamier and confhied by the metal cover-box for five hours, 

 destroyed all ants, and all stages, m the boxes. Mention is made 

 of the use of this fumigant on page 96. 



Other expermients made with the bisulphid of carbon showed 

 it to be the most available fumigant for the destruction of colonies 

 in accessible situations. 



When colonies are so situated that they can be fumigated with 

 bisulphid nothing is more effective for their destruction, but the 

 difficulty of applymg this measure Hes in the situation of colonies 

 hi aU sorts of inaccessible places (see list of nesting places, p. 55) 

 and to the fact that hi heavily infested areas the gaUeries of one 

 nest are practically continuous with those of others, affording many 

 ants the opportunity of escaping from the fumes. 



Such substances as hot water, kerosene, crude oil, etc., will, of 

 course, destroy the ants sprayed with them and often it is quite 

 practicable to use these substances for the destruction of colonies 

 that are discovered by turning over boards, pieces of wood, piles 

 of trash, etc. 



