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18

RESULTS AND DISCUSSION

Effects of the light dosage

The light dosages used were calculated at half the recommended strength figured as pounds of active chemical per 100 gallons (table I). A rather quick kill of earwigs was noted in the first series of experiments

which was conducted in the outdoor insectary. There were rather high temperatures and low relative humidites in this location. These factors unquestionably had adverse effects on the earwigs and created some doubt as to the reliability of experiment I. Experiments II and III were conducted in the greenhouse under quite favorable environmental conditions.

Immature earwigs in the third and fourth nymphal instars were used in experiment I. All of the insects were killed with all of the treatments by the end of 85 hours. These results are given in figure 3. Aldrin and chlordane showed a tendency to kill faster, but in the long run there was little difference between chemicals. Eight days following the initial treatments a second series of earwigs was introduced without renewing the strength of the insecticides. The results are given in figure 4. None of the treatments caused a complete mortality, but both dieldrin and heptachlor gave quicker results and a higher kill. All of the materials were still highly effective.

Later in the season with equal numbers of fourth instar nymphs and adults, the work was repeated in experiment I1. The procedure was the same as before except that the work was in the greenhouse and there were nine days between the first and second series. These results are shown in figures 5 and 6. The mortality was much slower in this