Published online by Cambridge University Press: 10 July 2009
A series of six substituted phenyl N-methylcarbamate insecticides were applied to laboratory-reared adults of G. morsitans Westw. as solutions in di-isobutyl ketone. Only the 2-isopropoxy and the 3-isopropyl compounds were toxic at 0·0068 µg. per fly and the former, being apparently more active, was evaluated more fully. It was found to be equitoxic with γ BHC to young flies, and not synergised to any significant degree by five parts of piperonyl butoxide. Pregnant flies were considerably more tolerant than young flies to low dosages but not to high ones. The suggested explanation postulates that the developing larva is a potential site of detoxification but that the rapid action of high dosages results in the death of the parent before the insecticide can reach the larva and be detoxified by it.