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51

In conclusion, it may be stated that dieldrin and aldrin show a wider separation in their degree of effectiveness with respect to one another than do chlordane and heptachlor. It may be further noted that dieldrin is the most widely separated from all the others, both from the standpoint of the initial inherent killing power and longer residual life.

A comparison of the effects of the light, medium and heavy concentrations of any one chemical reveals that the heavy dosage was, more rapid in effecting the highest kill. In contrast to this marked superiority of the heavy dosage, comparisons of the medium and light concentrations with one another show less difference in performance with equivalent results in the long run. The fact that the lighter dosages paralleled each other to a high degree and in most cases terminated by giving approximately the same per cent of kill, would suggest that they are equal in effectiveness in the end.

The number of recoveries recorded for individuals, that had at one time shown severe effects of the chemicals, was greater in the second and third experiments where later life stages of the insects were used

and where the environmental conditions were most favorable for keeping them active. On the other hand, there seemed to be no consistent difference in the total numbers which recovered in any given experiment from any specific chemical. It was shown that aldrin allowed the fewest recoveries, and was followed by chlordane and dieldrin showing equal effects, and heptachlor.

In the timed exposure experiment, the data indicate that there is a relationship between the effects of certain chemicals and the length of time that earwigs are exposed to them. The trend was for those