Location of the host

Abstract

The difficulty hungry blood-sucking insects have in locating their next blood meal depends upon the closeness of their association with the host. At one extreme we have the permanent ectoparasites which are in the happy position of having food continually ‘on tap’. Only by accident will they find themselves more than a few millimetres from the skin of the host and the blood that it holds. At the other extreme are those temporary ectoparasites, like blackflies and tabanids, which do not remain permanently in the vicinity of the host. When these insects are hungry their first problem is to locate the host, often a difficult and complex behavioural task. These differences in life-style are reflected in the number of antennal receptors which different types of blood-sucking insect possess (Chapman 1982); not surprisingly the more independent, host-seeking insects possess the most receptors. Thus, lice have only 10–20 antennal receptors and fleas about 50, but the stablefly, which spends most of its time at some distance from the host, has nearly 5000 antennal receptors. Considering two bugs, we see that Cimex lectularius has only 56 antennal receptors compared to 2900 on the more adventurous Triatoma infestans. Most of the detailed information on host finding is restricted to a small number of temporary ectoparasites and the discussion which follows will concentrate largely on these.