CONTACT insecticides as a class are lipoid-soluble, and it is reasonable to surmise that the first step in their uptake or pick-up by the insect might be generally their dissolution in the epicuticular waxes. All the same, experimental evidence of this phenomenon does not seem to exist, and relative solubility of insecticidal chemicals in cuticular waxes of insects has not been studied so far as known to us. Recently, it has been possible to develop a fairly handy technique for such studies and to collect thereby some experimental evidence of the existence of correlation between lipoid solubility and insecticidal action.