In the course ot laboratory tests with insecticides, some interesting data were obtained relative to the effect of certain materials upon the over-wintering egg masses of the Eastern tent caterpillar. The data appear to be of sufficient interest to warrant further study and are presented here with that purpose in mind.

A number of egg masses was collected. These were brought into the laboratory, were examined and sorted into lots roughly comparable in numbers. The twigs to be sprayed were segregated. Solutions of the following insecticides were then prepared.