DDT-Metabolism and Excretion in Coleomegilla maculata De Geer

Adults of the lady beetle Coleomegilla maculata De Geer, were topically treated with 40 μg of DDT. DDT and DDE were extracted with acetonitrile, partitioned with n-hexane, and determined by gas-liquid chromatography using an electron capture detector. DDT was metabolized to DDE. DDE [1,1-dichloro-2,2-bis ( P -chlorophenyl) ethylene] probably was the only metabolite of DDT, since most of the applied dose was accounted for as DDT and DDE. In addition to metabolizing DDT to DDE, these beetles resist DDT poisoning by excreting DDT and DDE in the feces and eggs as much as 5 μg of DDT-DDE were present in an average egg mass and as much as 1.1 μg of DDTDDE were excreted in the feces per day. For 3-4 days after DDT treatment, feces contained greater amount of DDT than DDE; after 5 days the quantity of DDE exceeded that of DDT in both feces and eggs. When lady beetles were topically treated with 40 μg of DDT, the dead insects contained about 1.5 to 2 times as much DDT as the surviving individuals. A large part of this difference was probably caused by the metabolism of DDT to DDE, since during the first 5 days after treatment with DDT, the surviving beetles contained more DDE than the dead individuals. Resistance of C. maeulata to DDT is due at least in part to its ability to metabolize DDT to DDE and to excrete these 2 compounds in feces and eggs.