Return to Publications List ◄ Next Page►

11

Laboratory experiments

Earwigs were obtained from baited traps and brought in fresh each time that they were to be used in experimental work. This eliminated the possibility of injury from a long period of handling.

Observation enclosures were petri dishes of 9.6 square inches total interior space into which were set wooden pot markers of 1.9 square inches exposed surface area. These markers had previously been soaked in a known concentration of the desired chemical. Whole wheat flakes plus a succulent green food material, and in some experiments a piece of wetted cellucotton was then placed inside the petri dish in preparation for the introduction of insects. In greenhouse experiments, the petri dishes were distributed over a course sand base which was kept saturated with water at all times, thereby lowering the temperature

and increasing the humidity of the experimental environment.

In one series of experiments, earwigs were exposed continuously to a known concentration of the four chemicals by using treated pot markers, which could be either contacted or avoided. Three experiments were conducted under different conditions. Each involved the light, medium and heavy concentrations of the four chemicals. The experiments were as follows:

1. In an outdoor insectary between the 4th and 19th of July, third and fourth instar nymphs were employed in equal proportions and observed under extremely variable environmental conditions, especially with respect to temperature and humidity. The food furnished to the insects contained a minimum of succulent material.

2. In a greenhouse between July 24th and August 15th, fourth in-star nymphs and adults in equal proportions were used in a carefully