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9

METHODS AND PROCEDURES

Trapping

In order to obtain the desired number of earwigs to be used in laboratory experiments, it was necessary to find proper methods for trapping them. The grooved board traps as used at Puyallup, Washington by Crumb and associates (1941) proved inadequate for trapping earwigs in a field experiment. The time of day, the degree of mechanical disturbance, wind velocity and moisture were factors that seemed to determine the total number of earwigs that could be found at any given time because they are free to enter and leave these traps at will. Although the board trap served admirably in supplying earwigs for laboratory experimental purposes, a different type of trap was desired for use in field experiments where total number caught was an important factor. This kind of experiment called for a single-entry, no-exit type of apparatus. A trap of this type was devised by using a pint sized mason jar to which an inverted wax paper cup, with its base removed, was firmly anchored by the ring part of the jar top (figure 1). The inside of the jar was spread with peanut butter to serve as bait, after which it was buried in the ground to one-quarter inch of its top. Entry could be made by even the smallest earwig nymph which might happen to be in the vicinity. The peanut butter scent attracted the insect to the rim where it fell down the sides of the paper cup and into the bottom of the jar.

After several trials with this kind of trap, it seemed that escapes could be reduced to a minimum by covering the bottom of the jar with a thin layer of whole wheat flakes and adding three or four milliliters of water from an eyedropper.