Original and generic products of 4% (W/W) permethrin emulsion were evaluated for their insecticidal effects on housefly Musca domestica adults, which had been collected at a cattle house on Ishigakijima Island, of the Yaeyama Islands, Okinawa prefecture, Japan. Thirty 3–5-day-old adult female houseflies were put in rectangular parallelepiped containers of which the top cover was stainless mesh. Then 100-, 200-, 400-, and 800-fold diluted emulsions of respective drugs were sprayed in amounts of 25 mL/m2, 50 mL/m2, 100 mL/m2, and 200 mL/m2. When less-diluted drugs were sprayed in larger amounts, the times until 50% flies were knocked down (KT50) were shorter and the knocked down rates were higher, reflecting dose-dependence. Among containers for which the same dosages of active ingredients were sprayed, KT50 were lower with larger amounts of drug solution, which demonstrated that quick-acting efficacy was achieved with larger spray amounts. Insecticidal effects of the two drugs, original and generic, were found to be equivalent from this study
