June, ’18] 
SWAIN: FUMIGATION EXPERIMENTS 
321 
45 foot, 8 ounce U. S. army duck. The ordinary earthenware fumi¬ 
gation pots and the form of sodium cyanide known as “Cyanegg” 
were used to generate the gas. 
The methods of procedure were identical in each case. Small cir¬ 
cular cardboard boxes (the common coverglass boxes), with the ends 
replaced with pieces of fine cheese cloth were used as containers for 
the insects. One was hung in each tent, about midway between top 
and bottom, and half the way from the center of the tent to the side. 
In those cases where red scale was used, the infested lemons were placed 
in a wire basket which was hung in the same position as the cages. 
The pot was set as near the center of the tent as possible, and the charge 
generated therein. Both “trees” were charged at the same time, al¬ 
though of course the insects from one were removed before those from 
the other. Although the “trees” were of the same size and shape, and 
the tents of the same material, the charges were alternated in each case 
in order to insure against any possible difference between them. 
In many of the experiments during the past season adult lady bird 
beetles (Hippodamia convergens) were used as an index for the “kill¬ 
ing efficiency.” For many purposes these were more advantageous 
than scale insects, but as results with scale insects were wanted, they 
were used to verify the results obtained with beetles. The beetles 
were used because it was easy to determine whether or not they were 
alive, inasmuch as they are active insects; because this could be de¬ 
termined accurately within a comparatively few hours after fumiga¬ 
tion; and because a considerable number of them could be obtained 
from the nearby mountains. All of the beetles used throughout the 
experiments were taken from two colonies in San Antonio Canyon near 
Camp Baldy. The main disadvantage with the beetles was the fact 
that they seem quite sensible to fluctuations in temperature. How¬ 
ever, as each set was carried on at the same time and under identical 
conditions, this was immaterial. The scale insect used to verify the 
results with beetles, was the common red scale of citrus ( Chrysom - 
phalus aurantii) on lemons from the Hewes Ranch near El Modeno, 
Orange County. 
In the experiments with the beetles four ounces of sodium cyanide 
were used in each charge, this being found sufficient to kill a large per¬ 
centage of the insects. A complete killing in any case was not]; de¬ 
sirable. With the scale insects it was found that a 2§ ounce charge 
was sufficient, a 3 ounce charge sometimes making a complete kill. 
Inasmuch as these “trees” called for a 6 ounce dose at the full schedule, 
it must be noted that these experiments were carried on in the day time, 
and that these “trees” were not filled with foliage as is the case in the 
field. 
