An apparatus for determining the relative toxicities of contact insecticides is described in detail. It is so arranged that successive batches of insects are sprayed under conditions as similar as possible, so that on using various substances at different concentrations, the results are directly comparable.

The apparatus consists of a glass jar in the lid of which an atomiser is fixed. By means of compressed air at known pressure the atomiser throws a constant quantity of fine spray upon insects placed in a dish inside the jar. Photographs illustrating the details of the apparatus are given.

The method used in practice for the spraying of aphides in this apparatus is described, and examples are given in the form of a table and a graph of the type of results obtained when different concentrations of nicotine are sprayed upon apterous agamic females of A. rumicis.