The Temperature Coefficients of DDT Action in Insects

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Abstract
Following external application, highly susceptible arthropods show either a positive or a negative temp. coeff. for mortality as a function of DDT concn. or dosage. At high concns. this is positive, at low concns. negative. Following injn. a positive temp. coeff. is always obtained, irrespective of dosage ( = concn.). DDT can be removed from colloidal suspension by arthropod cuticle and then recovered from the cuticle. The results of pretreatments at various temps. usually follow prediction. The data show that at low concns. DDT penetrates the arthropod cuticle more effectively at low temps. This negative temp. coeff. at low concns. is shown to be due to properties of the body wall, probably of the cuticle itself. Possible explanations are discussed.