Microbioassay of Insecticide Residues in Plant and Animal Tissues

Small shell vials closed by a screen top have been used as exposure chambers in evaluating the toxicity of organic insecticides to houseflies and in bioassaying for contamination of plant or animal matter with these substances. Treatment of a chloroform extract containing hexachlorocyclohexane or DDT with strong sulfuric acid and passage of the chloroform extract containing parathion through an absorption column greatly diminish the interference due to extractives from the plant or animal tissues. Data for LD 50 to female houseflies are given for parathion, γ-hexachlorocyclohexane, and p,p′ -DDT in terms of micrograms per vial and per square centimeter. Female flies require approximately twice the dosage needed for males. The small vial method is extensively used in following the development of resistance.