Distribution of Demodex aurati in the Host (Mesocricetus auratus) Skin Complex

All stages in the life cycle of Demodex aurati are found in the pilo-sebaceous component of the skin: mature adults of both sexes and ova at or above the opening of the sebaceous canal and larvae and nymphs below. No mites were found in either the anagen or catagen epithelial elongations. There appeared to be no correlation between mite life cycle and stage of hair development. Mites showed no preference for hair types nor any indication of migration in 21 days, even in heavily populated areas. Overcrowding led to distension of the hair follicle, and in a few cases, to melanocyte aggregation in the dermis around this distended area. Only adult mites (both sexes) were found to leave the hair follicle in segments of excised skin. These did not reenter hair follicles but either ascended hairs or wandered across the skin until they died. The probable sequence of life cycle events is detailed with suggestions of modes of migration and transference. Both migration and transference in Demodex aurati probably occur only in the adult stage of the life cycle. It is suggested that most topical drugs are inefficient for control of such demodicids as Demodex aurati since they fail to reach the deep-seated immature stages.