DEVELOPMENT OF DDT RESISTANCE IN CERTAIN MAYFLIES IN NEW BRUNSWICK

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Abstract
Populations of the mayfly Heptagenia hebe McDunnough in areas of New Brunswick air-sprayed with DDT for budworm control for eight successive years, when tested as nymphs taken from the streams, showed LC50 levels 3 times as high as those in untreated areas. Populations surviving an airspray in 1965 proved to be 12 to 40 times as DDT-resistant as the normal. Pre-spray populations of Stenonema fuscum (Clemens) showed a 5-fold resistance, and post-spray populations of Stenonema interpunctatum (Say) showed a 10-fold DDT resistance when those from treated areas were compared with those from untreated. The DDT-resistant nymphs of H. hebe detoxified DDT to DDE 15 times faster than the normal nymphs; DDE was also the metabolite in S. interpunctatum. In both these species the DDT-resistant nymphs absorbed roughly twice as much DDT as the normal.