Return to Publications List ◄ Next Page►

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