METHODS OF REPRESSION. 83 
cover-box for the introduction of the chemicals used in fumigating. 
Just beneath this opening, which could be closed practically air-tight, 
was placed the usual earthenware crock for holding sulphuric acid 
and water. Experimental fumigation of these boxes was commenced 
with a charge of \ ounce of 98 per cent potassium cyanid and the 
requisite amounts of water and sulphuric acid. This strength was 
fourd not to kill any ants in the box except those which were actually 
outside the packing at the time of fumigation. Gradually this 
charge was increased until as much as 4 ounces of cyanid were used 
at a time in the inclosed space of 22 cubic feet. Even at this strength, 
which corresponded to 18 ounces of cyanid per 100 cubic feet, ants 
more than 8 inches from the outside of the box were not affected by a 
confinement 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 examined 
and it was found that only those within a couple of inches 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 accordingly undertaken with bisulphid of 
carbon for destruction of the ants in the boxes. Holes were made to 
the very bottom of the contents, bisulphid poured into 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 manner and confined by the metal cover-box for five hours, 
destroyed all ants, and all stages, in the boxes. Mention is made 
of the use of this fumigant on page 96. 
Other experiments 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 then destruction, but the 
difficulty of applying this measure lies in the situation of colonies 
in all sorts of inaccessible places (see list of nesting places, p. 55) 
and to the fact that in heavily infested areas the galleries 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. 
