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Date of Award


Document Type


Degree Name

Master of Science (M.S.)


Graduate Studies

First Advisor

Alice S. Hunter

Second Advisor

James Sanborn


A laboratory colony of a multi-insecticide susceptible strain of the housefly, Musca domestica was challenged with continuous larval selection pressure equivalent to the initial LC 60 level for 8 generations with the insect growth regulator WL 86303 (1-(3,5-dichloro-4)4-nitrophenoxy- phenyl)-3 -(2)chlorobenzoyl)- urea). A more than twofold increase in resistance was observed at the F8 generation. No cross-tolerance to the related compound, diflubenzuron (DIMILIN (R)) (1-(4-chlorophenyl)-3- (2,6-difluorobenzoyl)-urea) was observed after 8 generations. WL 86303 was significantly less toxic to houseflies than diflubenzuron. No significant difference was noted between the toxicity of WL 86303 to an unpressured wild housefly strain, and to the unselected multi-susceptible strain. A larval-rearing bioassay technique for measuring the toxicity levels of juvenile developmental disruptors is described.



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