92 
THE ARGENTINE ANT. 
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lit? 
S^r.i 
oranges of exceptionally high quality, and the industry has proven a 
paying one for many years past. A considerable number of localities 
have during the past 15 or 20 years become infested by the Argentine 
ant, due, no doubt, to drifting logs containing ant colonies that 
lodged along the banks of the river. The warm winters, coupled with 
the presence of considerable moisture at all times, have made possible 
very rapid increase of the ants, and the first result of their activities 
has been a greatly accelerated rate of increase by all scale insects, and 
particularly by the chaff scale (Parlatoria pergandii Comst.). Not 
only do the ants protect this scale from its natural enemies, but they 
colonize the larvse up- 
on the young growth 
of the orange trees and 
upon trees not pre- 
viously infested. 
At times the ants 
eat into the orange 
buds, evidently in 
quest of nectar, and 
buds thus injured do 
not set fruit. This 
habit is not always 
exhibited by the ants, 
and it may be that it is 
more or less dependent 
upon the prevalence 
of scale insects on the 
trees. The secretions 
of aphides and scale 
insects are preferred 
to other food, and it 
seems not unlikely 
that when honeydew 
is abundant the buds are not molested by the ants. Whether 
or not the ants do any other direct damage to the trees is still 
an unsettled question, but certain it is that the bearing qualities 
of an orchard are seriously impaired by the second season of 
infestation, the crop is almost entirely lost by the third season, 
and the trees are dying rapidly by , the fourth year of infesta- 
tion. (See PI. VIII.) One orchard which well illustrates the rate 
of destruction consisted of a 20-acre tract of young grapefruit 
trees, visited by the authors in March, 1910. The trees at this 
time were about 4 to 5 feet in height and appeared very vigorous and 
healthy. The ants were, however, rapidly infesting the field from 
adjoining orchards. During the summer of 1910 the ants increased 
i 
f&. 
Fig. 13. — Sectional view of ant-proof hive stand from above, show- 
ing construction. (Senior author's illustration.) 
