THE ARGENTINE ANT IN RELATION TO CITRUS GROVES. 37 
experiments to determine the effect of the ants. In a test conducted 
upon } 7 oung orange trees colonized with the scales, two of the trees, 
on which there were 5,425 and 334 young scales, respectively, were 
banded to exclude ants, while a third, on which there were 3,100 
scales, was left accessible to the ants for comparison. The number 
of scales gradually diminished on all the trees, accompanied by a cois 
responding increase of parasitized scale remains, until within two 
months from the time of starting the experiment practically all had 
been destroyed. 
The destruction of these scales was caused almost exclusively by 
parasites, the percentage of parasitized scales increasing, with slight 
fluctuations, at the same rate on the tree frequented by ants as on the 
two trees from which ants were excluded. There was nothing in the 
condition of the trees or in their suitability as a food plant of this 
scale to prevent the scales from thriving, as was shown by the fact 
that a few sound scales which had secured perfect shelter from para- 
sites remained on the trees as late as October, three and one-half 
months after all those not sheltered had been destroyed. 
It was plainly seen in this experiment, and many other observa- 
tions bear out this conclusion, that the internal parasites are the 
most effective enemies of the soft brown scale in Louisiana and that 
the Argentine ant does not extensively prevent the work of these 
insects. A considerable number of adult parasites were seen on these 
trees during the examinations, and fully as many on the ant-invaded 
trees as on the noninvaded ones. Two species of chalcids, 1 viz, 
Eupelmus coccidis Gir. and Coccojiliagus ooccidis Gir., were reared 
from ant-attended soft brown scales in Louisiana. 
While an orange tree occasionally would be found in Louisiana 
with one or more small branches very heavily infested with the soft 
brown scale, assiduously attended by the ants, the worst infestations 
that came to notice were on plants other than citrus. For example, 
in an orange grove at Buras, where this scale was present in small 
numbers and scattered on orange trees, one limb of a rosebush was 
found infested so severely that in a space 1 foot long on a branch 
about one-eighth inch in diameter there were 1,440 scales. 
Large groups of this sort sometimes are found in which there is 
very little evidence of parasitism, but usually from 2 to 60 per cent 
or more of all the scales occurring in such groups either contain the 
parasites or show their exit holes. 
The soft brown scale undoubtedly is held in check in Louisiana 
orange groves, regardless of whether ants are present or not, by its 
natural enemies and particularly by the internal parasites. 
identified by Mr. A. A. Girault. 
