The doses lethal to 50% of the insects (LD50 values) obtained for a strain of Hydrotaea aenescens (Wiedemann) adults from a layer farm revealed higher sensitivity to 16 insecticides than those recorded for the susceptible WHO/SRS strain of the housefly. Because H. aenescens adults are about half the size of the housefly, the chemical compounds used for adult control may jeopardize the survival of Hydrotaea populations released in animal confinement houses. An efficient and economical combined application of biological and chemical control methods is possible only if the local management conditions and the dissimilar behavior of the adults of the two species are taken into consideration during the use of insecticides. Other suggestions and implications are further discussed.