Absorption and Metabolism of DDT in the Boll Weevil1

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Abstract
The basis for the natural tolerance of the boll weevil (Anthonomus grandis Boh.) for DDT was studied by treating weevils topically or by injection and determining the rate of penetration and metabolism of DDT. The weevil has a natural tolerance for DDT which varies with the strain, age, and time of year collected. Overwintered weevils are more sensitive than first generation populations. Weevils resistant to chlorinated hydrocarbons, such as endrin, are slightly more resistant to DDT than endrin-susceptible weevils. Both resistant and susceptible weevils are very susceptible to injected dosages of DDT. The rates of absorption in susceptible and resistant boll weevils are equal; about 60% of a 5 µg. dosage being absorbed in 48 hours. Small amounts of DDT are found in both strains, but slightly more in the susceptible insects. DDE is produced in trace quantities by both strains. After 48 hours about 40% of the applied DDT is converted into unknown metabolites. Neither DDE nor DDA is involved in the primary avenue of DDT detoxication. Compounds reported as outstanding DDT synergists in the house fly increase the toxicity of DDT in the weevil only three- to five-fold. DDT is more toxic to the weevil at lower temperatures.