Toxicity of DDT to the American Cockroach When Lipid Content and Temperature are Varied1

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Abstract
The mortality of male and female Periplaneta americana was more readily accomplished, after injection with DDT, at a lower post-treatment temperature (15[degree]C) than at a higher one (30[degree]C). The LD50 values (using micrograms per gram of roach) on a low protein diet were, for males, 1 at 15[degree]C and 9 at 30[degree]C; with a high protein diet, 0.4 at 15[degree]C and 5.9 at 30[degree]C; with a dog pellet diet, 1.7 at 15[degree]C and 10.5 at 30[degree]C. For females LD50 values expressed in the same order were with low protein, 3.1 and 41; high protein 1.2 and 21; dog pellet diet 5.3 and 58. Thus, the magnitude of differences between the 2 temperature extremes ranged from 6 times to 17.5 times. female roaches were more resistant than males when compared on similar diets at the same temperatures. The LD50 values for females were 3 to 5 times higher than for males. Ether extractions of the cockroaches showed that the high protein diet had produced individuals with the lowest lipid content. The dog food diet produced roaches with the highest lipid content. Toxicity values based on micrograms of DDT per milligram of lipids were compared with values based on micrograms of DDT per gram of body weight. Regression lines from values based upon lipid content had a somewhat steeper slope than those based upon body weights. However, there was no indication that the quantity of lipids present could be responsible for or related to the higher mortality occurring at the lower (15[degree]C) post-treatment temperature. Further, differences in quantities of lipids between sexes do not appear sufficiently large to explain the sex differences which occur in response to the action of DDT.