96 THE ARGENTINE ANT. 
first made in fumigating the boxes with hydrocyanic-acid gas (see 
pp. 82-83), but these were not successful. Carbon bisulphid was next 
tried, with perfect success. Delay in obtaining a sufficient supply 
of bisulphid resulted in delayed treatment of many of the boxes, 
and doubtless some of the colonies escaped as the weather became 
warmer in the early part of February. Nevertheless, the number 
of queens and workers destroyed ranged into the millions. The 
owner wished to deal the ants the hardest blow possible, so early 
in the spring he flooded the orchard, drove the remaining ant colo- 
nies to the boxes, and fumigated these the second time. 
The results of this work were eminently satisfactory. The orchard 
was first infested by the ants in 1909. In 1910 they reached enor- 
mous numbers; chaff and purple scales increased until the trees were 
almost encrusted, and many of the trees showed signs of failing. 
The foliage began to turn yellow, and the crop of 1910 fell off 
severely, in spite of the flooding that was done by the owner in the 
spring of 1910. During the summer of 1911, following the use of 
the trap boxes, the orchard improved remarkably, and the crop was 
up to the original production. It was found that when the boxes 
were left in the orchard ant colonies took up their abode therein 
during the summer months; for this reason these boxes were fumi- 
gated with bisulphid from time to time. An examination of the 
orchard in January, 1912, showed that the infestation by the chaff 
scale had been greatly reduced by diminution of the ants, even 
though the owner had done no spraying for destruction of the scale 
insects. The ant infestation showed some increase in the autumn 
of 1911, but the orchard had returned to its normal healthy condi- 
tion, and it was evident that a continuation of these methods would 
insure good crops indefinitely. A view of this orchard, taken in 
January, 1912, is shown in Plate XIII. 
One important point came to light in these experiments, and that 
was the necessity of placing the trap boxes in position early in the 
autumn so that the vegetation in them would be decaying well at 
the approach of cool weather in November. With considerable 
decomposition going on at the time the ants are seeking winter 
quarters, the warmth of the box becomes very attractive to them. 
The use of arsenicals and other poisons in the infested orange 
groves was found impossible, for the reason that the secretions of 
scale insects and aphides are preferred by the ants to all other foods. 
