Blood-sucking insects feed from a range of different host animals; because of the bites we receive we are acutely aware of the fact that many of them feed from humans, but many other animals are also exploited, including other mammals, birds, reptiles, amphibians and fish, and even insects, arachnids and annelids (Hocking, 1971). Any one insect does not feed equally well from all of these potential resources; it displays host choice. For some insects, particularly some permanent ectoparasites, the host choice may be very specific. Occasionally, for example for human lice, just a single species. For other blood-sucking insects host choice is clearly not as restricted as introduced exotic hosts (e.g. those in zoos) quickly become incorporated into the diet of local blood-sucking insects.
Let us consider what is meant by host choice. In its main sense it denotes the species of host animal or animals from which blood-sucking insects obtain their blood meals. But host choice can go beyond particular species of host chosen. Insects often choose to feed on particular individuals from among preferred species, which may well have implications for disease transmission (Burkot, 1988; Kelly, 2001; McCall and Kelly, 2002).
Although most blood-sucking insects in their undisturbed, natural surroundings show a preference for feeding from a particular group or species, or even a primary cohort of their chosen species, the degree of host specificity shown varies greatly from one type of insect to the next.