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20 In the first series of experiment I (figure 9) a rapid
kill was, achieved with all chemicals.
The second series of earwigs, introduced three days after the first
treatments, was killed off faster by dieldrin than any other chemical. This was followed by aldrin, chlordane and heptachlor
in descending order of effectiveness, as is shown in figure 10. A third series of insects introduced six
days after the initial treatments gave 90 per cent kill or better with all chemicals. These results
are given in figure 11. In the second experiment, all chemicals produced a
better than 80 per cent kill with dieldrin and aldrin exceeding the others,
as shown in figure 12. The second
series, begun 20 days after the initial work was started, resulted in a poor
kill with all chemicals except dieldrin which killed 76 per cent of the earwigs. Heptachlor, chlordane and aldrin followed
with 17, 14 and 11 per cent, respectively. These figures are presented in figure
13. In the third
experiment the effectiveness of all chemicals was considerably less than in the
previous two experiments. Figure 14 shows that dieldrin exceeded
all other chemicals by producing a 75 per cent kill. It was, in turn, followed by chlordane,
aldrin and heptachlor which gave 55, 41 and 39 per cent kills, respectively.
In the second series, which was initiated 22 days after the first series,
dieldrin had little effect; and all other chemicals were below 12 per cent in
effectiveness. These results may be seen
in figure 15. Action of the heavy dosage Calculation of the heavy dosages was made at twice the
medium dosage; and as would normally be expected, showed an increase in |