Defensive behaviour is one of the principal ways vertebrate hosts regulate the blood-feeding success of vector insects. Intrinsic variation in the intensity and efficiency of this biting avoidance behaviour depends on host: (1) species, (2) size, (3) age, (4) health and (5) individuality. In this paper we summarize data on the relative importance of each of these host-associated factors in regulating mosquito feeding and transmission of mosquito-borne diseases.