THE ARGENTINE ANT IN RELATION TO CITRUS GROVES. 
29 
after the mealybugs had become located, the ants were excluded 
from 3 of the plants on which there were 4,573 young bugs and 
allowed free access to the remaining 3, on which there were 3,094 
mealybugs. On August 21 there were only 577 mealybugs left on 
the plants from which ants were excluded, 40.6 per cent of the 
leaves being infested with an average of 3.2 mealybugs each ; whereas 
on the plants traversed by ants there were 5,461 mealybugs, 74.5 
per cent of the leaves being infested with an average of 29 mealy- 
bugs each. 
Experiment V. 
In the fifth experiment, which was conducted at Duarte, Cal., it 
was demonstrated that the effect of the ants in increasing the abund- 
ance of mealybugs may be largely neutralized in the presence of un- 
checked infestation by the black scale (Saissetia oleae Bern.). Ten 
bearing naval-orange trees of about equal condition and equal 
mealybug, ant, and black-scale infestation, the last-named being 
heavy, and with fully 90 per cent of sooting of the leaves, the trees 
not having been fumigated since 1913, were selected for this experi- 
ment. On April 20 five of the trees were banded with adhesive mix- 
ture to exclude ants, and the alternating five left accessible to ants 
for comparison. The results of this experiment are summarized in 
Table VI. 
Table VI. — Effect of the Argentine ant on abundance of mealybugs on orange 
trees heavily infested tuith the black scale (Saissetia oleae). Los Angeles 
County, Cal., 1916. 
e. 
Ants present. 
Ants excluded. 
Mealybug infestation. 
Mealybug infestation. 
Dat 
On fruits. 
On other parts of 
On fruits. 
Total 
number 
Total 
num- 
ber ex- 
amined. 
On other parts of 
Num- 
ber in- 
Per 
cent in- 
trees. 
Num- 
ber in- 
Per 
cent in- 
trees. 
ined. 
fested. 
fested. 
fested. 
fested. 
Per ct. 
Per ct. 
May 
25 
100 
80 
80 
Many scattered 
mealybugs and 
100 
94 
94 
Many scattered 
mealybugs and 
small groups. 
small groups. 
July 
7 
437 
156 
35.6 
11.4 per cent of new 
shoots infested. 
304 
165 
54.2 
33.1 per cent of new 
shoots infested. 
July 
21 
455 
154 
33.8 
51 groups of 1 to 30 
young and 17 adults 
with egg masses. 
382 
193 
50.5 
36 groups of 1 to 15 
young and 47 
adults with egg 
*Aug. 
masses. 
15 
409 
143 
34.9 
81 groups of 1 to 5 
376 
165 
43.8 
20 groups of 1 to 5 
mealybugs each. 
mealybugs each 
Sept 
11 
364 
198 
54.5 
79 groups of 1 to 5 
mealybugs each. 
340 
137 
40.2 
41 individual 
mealybugs only. 
