480 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 13 
The above table presents the results of experimental work in which 
five orange trees of equal size infested with immature black scale 
were fumigated with liquid hydrocyanic acid according to the same 
dosage schedule and for the same exposure. Two trees were covered 
with tannin-treated (dark colored) 6j-ounce drill and three trees were 
covered with 8-ounce untreated duck. The results of the fumigation 
show that the dark-colored tents gave the best scale-kill, this superi¬ 
ority being most evident on the north side of the tree. This difference 
in mortality in favor of dark-colored tents was even more effectively 
brought out where the maximum scale-kill departed more widely from 
the point of eradication than for the above trees. For instance, one 
set of trees given a 30-minute exposure averaged 95 per cent scale-kill 
on the shaded side of the trees fumigated under dark-colored drill 
tents but showed only 76 per cent scale-kill at the same position on 
trees fumigated under untreated duck tents. 
This difference in scale-kill between the dark and light tents appeared 
attributable to the higher temperatures within the former. This 
condition is shown by the following table in which is recorded the 
temperature at different points within a tannin-treated drill tent as 
well as a white army duck tent. 
Table IV—The Comparative Temperatures at Different Parts of Two 12-Foot Trees, One 
Covered with a 6§-Ounce Tannin-Treated (Dark Colored) Tent and the Other Covered 
with a White 8-Ounce Army Duck Tent. May 18, 1920, 9-10 a. m. Records Made at 10 
Minute Intervals. Thermometers 6-8 Inches from Tent 
Time 
Outside temp. 
Sunward 3J 
ft. 
Sunward 11 ft. 
Shade (N.) 3| ft. 
Middle 3 ft. 
Sun 
Shade 
Dark 
tent 
Light 
tent 
Dif. 
Dark 
tent 
Light 
tent 
Dif. 
Dark 
tent 
Light 
tent 
Dif. 
Dark 
tent 
Light 
tent 
Dif. 
Start. 
82° 
78° 
10 min.. 
85 
79 
90° 
87° 
3° 
97° 
95° 
2° 
84° 
79° 
5° 
83° 
79° 
4° 
20 min. 
85 
80 
93 
89 
4 
104 
101 
3 
87 
81 
6 
86 
82 
4 
30 min. 
87 
82 
95 
90 
5 
108 
104 
4 
89 
82 
7 
88 
82 
6 
40 min. 
88 
83 
98 
91 
7 
110 
106 
4 
90 
83 
7 
89 
83 
6 
50 min. 
86 
85 
97 
91 
6 
110 
106 
4 
91 
84 
7 
90 
84 
6 
60 min. 
89 
85 
99 
92 
7 
112 
108 
4 
92 
85 
7 
91 
85 
6 
Not only is the temperature higher at all points within a dark col¬ 
ored tent, especially on the shaded side where the average difference 
amounts to 6 or 7 degrees, but there appears to be an influence on the 
gas diffusion due to the heat factor which interferes with its escape 
through the tenting and this influence is most apparent under the 
darker tent. So noticeable is this difference in gas retention between 
the tw r o types of tents that it is readily detected by the smell at the end 
of a normal exposure. In our experimental work during the winter it 
was observed that one could stay beneath an 8-ounce untreated duck 
