Storage Fungi Antagonistic to the Flour Mite (Acarus siro L.)

Under favourable physical conditions, populations of the flour mite. Acarus siro L., on wheat germ flakes normally eat the whole of the food supply, and then die out unless the food is replenished. But sometimes the germ becomes discoloured (brown) and the mites die out leaving the greater part of it uneaten. The discoloration and the premature failure of the mite populations are both caused by the xerophilic mould Sporendonema sebi Fr. Aspects of the decline are reduced reproduction, high mortality and retarded development. Since the antagonistic effect is not noticeably diminished in re-sterilized material, it must be possible for it to be exerted either by the dead fungus or through an effect of the fungus on the food, or both. Another xerophilic species, Aspergillus restrictus, also causes the premature failure of flour mite populations, and a different discoloration of the germ flakes. When the infected material is re-sterilized, the mites may consume the whole of it, but abnormally slowly. While this mite, like related species, uses many moulds as food, some are evidently harmful to it, either because they are themselves poisonous or because they have some harmful effect upon the food.