Ever since the slogan "Swat the fly" was liberated on the American public, the hygienic danger of the house fly has been thoroughly understood by persons in almost all walks of life. The injunction to destroy all evident specimens of this insect species has been heeded far and wide. In thousands of homes the fly is no longer tolerated. The logical solution of the fly problem resides, however, in the elimination of all breeding places or the destruction of the eggs and maggots before they can develop into an adult age.
Horse manure, which forms the principal breeding place of the house fly, has a large value as a fertilizer. It is not difficult to find a larvicide which will be effective; but to be suitable it must destroy the larvae of the fly without killing the bacteria of the manure. The latter are essential for the proper conversion of