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The Contact Toxicity of a Number of D.D.T. Analogues and of Four Isomers of Benzene Hexachloride to Macrosiphoniella San Born I and Oryzaephilus Surinamensis *
Author(s) -
Lord K. A.
Publication year - 1948
Publication title -
annals of applied biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 80
eISSN - 1744-7348
pISSN - 0003-4746
DOI - 10.1111/j.1744-7348.1948.tb07394.x
Subject(s) - oryzaephilus surinamensis , toxicity , biology , benzene , stereochemistry , toxicology , insect , chemistry , organic chemistry , botany
Twenty‐three analogues of D.D.T. and four isomers of benzene hexachloride have been compared with D.D.T. for toxicity as contact insecticides using a direct spraying technique. Each substance has been tested against two insect species: Macrosiphoniella sanborni and Oryzaephilus surinamensis. The substances tested included a number of halogen and alkyloxy analogues of D.D.T. and a number of compounds of varying degrees of chlorination between diphenylethane and D.D.T. The biological data have been examined, as far as possible, by the method of probits. The probit lines for the D.D.T. analogues varied both in position and in slope: those for the isomers of benzene hexachloride in position but not in slope. In general, neither the relative positions nor the relative slopes of the probit lines for the various substances were the same against the two insect species. The toxicity of substances analogous to D.D.T. appears to be related to molecular weight, with maximum toxicity occurring in the molecular weight range 300–450. Among D.D.T. analogues the slope of the probit line is apparently correlated with molecular volume. The variation of the slope of the probit lines has been discussed, and it has been concluded that it arises from differences in the interaction of the poisons with the test‐subjects. The various theories relating to the toxicity of D.D.T. and B.H.C have been discussed in relation to the experimental data described here. To account for all the experimental results by means of one theory it is necessary to postulate a physico‐chemical mechanism of toxic action. Such a mechanism implies that the intensity of biological action will be dependent upon the physico‐chemical properties of the poisons, whether or not a specific molecular configuration is involved, and toxicity is therefore dependent on the molecule as a whole.