EN
Insecticidal activity of B. thuringiensis subsp. morrisoni and B. thuringiensis subsp. darmstadiensis as well as B. sphaericus 2362 and 2297 was evaluated against larvae of the house fly (Musca domestica) under laboratory condition. The activity of all tested strains was similar, LC₅₀ ranges from 4 x 10⁷ to 1 x 10⁸ spores/ml. The higher spores conentration (2 x 10⁹) caused ca 70 per cent mortality. The relative low sensitivity of house fly larvae could results from weakly alcalic pH of the gut (7.6-7.8).