Abstract The feeding mechanism of Chiroptonyssus robustipes , (Acarina: Macronyssidae) as observed in the living tissue of the bat wing, is described. Only the protonymphs and the adults feed on the host, Tadarida braziliensis mexicana . The protonymphs feed for 10–12 hours and probably more, on tissue fluids. Shortly before leaving their host, they engorge rapidly on blood which they obtain by rupturing a venule. The females take only blood and feed rapidly by teasing a hole in the wall of a small venule, a method resembling that of the tsetse fly. The areas of the wing where the protonymphs feed show pronounced changes. The stratum corneum is delaminated and there is a marked dermal edema. When injected into the blood stream of the host Evan's blue passes rapidly into the gut of the mites, indicating an increased permeability at the site of feeding. This increase in the production of tissue fluids undoubtedly facilitates the mites' feeding.