126 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 13 
In all, nine series of experiments, such as described above, were 
made. Each “series” consisted of one cage-covered cotton plant 
treated with lead arsenate, one with calcium arsenate and one check 
cage, the latter containing the same number of weevils used in each 
of the other cages, in order to determine the “natural” mortality. 
Observations were made twice daily on 750 weevils confined on 
plants treated with lead arsenate, 750 on plants treated with calcium 
arsenate and 750 confined on non-treated cotton plants but which 
were otherwise under the same conditions as those on the treated plants. 
The following table shows the daily mortality, in percentages, among 
the weevils on plants treated with lead arsenate when protected from 
dew and rain, namely, kept entirely dry during the course of the 
experiments, and on plants similarly treated which were exposed to 
normal deposition of dew and light rains, being protected only from 
severe storms. 
The deposition of dew on the exposed plants was of almost daily 
occurrence, heavy dew occurring on 20 mornings, medium dew on 17 
mornings, light dew on 9 mornings and no dew on 10 mornings during 
the 60 “experiment-days” that these investigations were under way. 
Light rain fell on one morning. During the course of the experiments 
only one storm occurred which required the covering of the cages 
which were under “normal” conditions as to precipitation of dew 
and rain. 
Of the nine plants treated with lead arsenate, three received the 
poison by the direct application or “blast” method and six by the 
“cloud” method as advocated by Coad. Of the three receiving treat¬ 
ment by the former method one was protected from all dew and rain 
and two were exposed to normal precipitation. Of the six treated by 
the cloud method two were protected from dew and rain and four 
exposed to normal precipitation. 1 
Poison used 
Method of 
application 
Number of 
weevils 
Mortality during 
10 days, per cent 
Lead arsenate. 
Blast 
150 
88.6 
Lead arsenate. 
Cloud 
600 
74.7 
Calcium arsenate. 
Blast 
150 
79.3 
Calcium arsenate. 
Cloud 
600 
74.2 
Check. 
None 
750 
16.1 
1 Although the primary object of these investigations was to determine how the weevil obtains suffi¬ 
cient poison to produce death, the experiments were, nevertheless, so arranged as to give data on other 
questions. The data have been tabulated, for example, to show the mortality resulting from applica¬ 
tion of lead arsenate by the blast or direct method and by the cloud or settling method; also to show the 
comparative mortality when calcium arsenate was applied by both these methods. This information is 
summarized in the following table which shows the mortality among the boll weevils during the first 
10 days following the applications: 
