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Toxicological studies on a beetle, Alphitobius laevigatus (F.)
Author(s) -
HEWLETT P.S.
Publication year - 1962
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.1744-7348.1962.tb06015.x
Subject(s) - biology , dieldrin , toxicant , toxicology , mealworm , zoology , larva , botany , pesticide , toxicity , ecology , chemistry , organic chemistry
SUMMARY As a first stage in obtaining information basic to full interpretation of experiments involving topical dosage of insects, relations between quantal response and two dose factors, concentration of toxicant and volume of solution, have been examined. The test insects, lesser mealworm beetles, Alphitobius laevigatus (F.), were dosed with solutions of n ‐valeryl 1,3‐indandione ( n ‐valone), DDT, dieldrin, and allethrin in a non‐volatile mineral oil, Shell Risella 17. Drops of 0.02‐0.10μl. were shot on to the mesoscutella of the beetles by an improved form of the air‐pulse micro‐drop applicator described by Hewlett (1954 a ); the beetles were positioned by means of a micromanipulator designed for the purpose. Control over the drop size was better than that by the previous applicator, as shown by an improved version of the immersion method of drop measurement used before. Beetles retained their doses satisfactorily, though transfers of minute quantities of solution between dosed beetles caged together, were shown to be possible. The toxicants appeared to act by contact only. Under certain conditions, which were avoided, the responses of individual beetles dosed with dieldrin or allethrin and caged together were not independent, probably because active beetles disturbed those affected. The toxicants differed markedly in the signs of poisoning that they produced and in speed of action, though none induced appreciable hyperactivity of the beetles. However, for investigating dose‐response relations, ‘end‐point mortalities’ or a near‐equivalent were determined. Planes for regression of probit response on log concentration and log volume fitted the data satisfactorily. For DDT and allethrin the coefficient for regression on log concentration was significantly higher than that on log volume; for dieldrin the difference was not significant, and for n ‐valone the results were variable. The estimate of the LD50 for DDT, in terms of μg. DDT per beetle, was about 50% higher when the DDT was applied in 0.08 μl. of solution than when in 0.02 μl.; the corresponding figure for allethrin was about 30%. The greater toxicity of the more concentrated solutions is discussed. Houseflies, Musca domestica (susceptible strains), appear to be more susceptible than A. laevigatus to DDT, dieldrin and allethrin.