In the first section of this review, the stimuli involved in orienting biting flies to their hosts from a distance are discussed under the following headings: (1) Appetitive search—driven by endogenous rhythms and hunger. (2) Activation—the switchover from search behaviour to active host-location brought about in the insect by host-originating stimuli including, depending on species, carbon dioxide, visual contact, and specific host odours. (3) Attraction—the process of active host-location through which the insect comes into the immediate vicinity of the host. This relies on host-originating stimuli including visual contact and olfactory stimuli such as carbon dioxide, volatiles such as acetone, and specific, usually very potent host-related odours.
The second part of this review discusses the properties of the odour plumes biting flies rely on to locate the host. Possible methods of host-location using air-borne odour plumes are presented and the “positive anemotaxis” model based on moth pheromone work is stressed.