The genus Acarus includes species that primarily inhabit nests of warm-blooded animals: mostly rodents and birds, but they are also peridomestic. These species are serious pests of stored products, primarily infesting grain and flour. Some species infest cheese (Fig. 15). Phoretic hosts include various arthropods (e.g., beetles, flies, fleas, and large mites).
Five species have been recorded from nests of European honey bee (Apis mellifera): Acarus farris, Acarus gracilis, Acarus immobilis, Acarus siro, and Acarus tyrophagoides. In addition, Acarus siro has been found in nests of Apis cerana and Bombus pascuorum. Acarus farris was the third most common species of Astigmata found in beehives in Poland (after Glycyphagus domesticus and Carpoglyphus lactis). In beehives Acarus species prefer pollen and bee bread, followed by bee hive debris. More rarely Acarus species occur on combs, wax, dead brood and bees, and mold. A few species can reproduce on propolis (A. immobilis) and honey (A. siro) but none on royal jelly (Chmielewski, 1991c).