CONTROL OF ARGENTINE ANT IN CALIFORNIA. 25 
Crystallization. — The sirup prepared with the formula used in 
orchards A and B commenced to thicken in from two to four weeks 
after its distribution in the orchard and crystallization started in 
from six weeks to two months. Sirup distributed in the dry cold 
weather of late fall was observed to crystallize in some cases within 
a month. The sirup proved less attractive to ants as it thickened, 
and crystallized sirup was little attended. Although the Barber 
formula proved very effective against the ants under conditions where 
heavy feeding followed the initial distribution, and control was really 
effected during the period of normal stability of the sirup, as was 
the case in orchards A and B, weather conditions and normal food 
supply of the ants frequently were such that feeding was slight 
during the early weeks of distribution. If in such cases the sirup 
became crystallized within a month or six weeks following the dis- 
tribution its effectiveness against the ants was greatly reduced. 
The situation is well presented by the comparison of ant control 
in a 10-acre orchard adjacent to orchard B, at Upland. The orchard 
consisted of 676 trees, 76 of which were reserved for control by 
another system. Ant control by the same sirup as used in orchard B 
was started in the remaining 600 trees, which were largely navel 
oranges with ant infestation practically identical with that in orchard 
B. The distribution took place during the first part of November, 
or fully a month later than in orchard B, and the sirup crystallized 
within a month after being put out. Although above 99 per cent of 
the trees in orchard B were free of ants on March 24, 1918, in this 
latter orchard only 65 per cent were in this condition. The differ- 
ence in control is attributable to a shorter period of sirup supply. 
This crystallization of sirup led to experiments in an effort to secure 
a sirup of greater stability and possibly more attractive to the ants. 
MODIFIED BARBER FORMULA I. 
Observations indicated that sirup which had become diluted by 
rain entering the container was more stable than the more concen- 
trated sirup. This led to the use of a modified formula in which the 
sugar was reduced from 15 pounds to 12 and the honey increased 
by one-half pound to compensate for the reduced sweetness. Experi- 
ments with this sirup during 1918 proved it to be as attractive to ants 
as the original formula and its stability was greatly increased, for 
during the summer it remained without crystallizing for periods up 
to four months. This sirup was used over a great acreage during 
1918 with marked success. With the approach of cold weather it 
was found that this sirup would crystallize, though much more slowly 
than the thicker sirup. 
Unboiled sirup. — An experiment was started on 50 trees in which 
the modified Barber formula was prepared without boiling, the sugar 
