Black fly interactions with their hosts
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Haematophagous black flies (Diptera: Simuliidae) seek mammal and bird hosts as blood sources and are responsible for significant human and animal hardship and economic loss due to annoyance, effects of biting and disease transmission. Simuliids locate and choose their hosts by orienting to host-originating chemical, visual and temperature stimuli. Little is known about the nature of the stimuli involved as chemical mediators though carbon dioxide is influential and certain other breath and body odours also clearly play roles. Effects of visual stimuli are limited to the effective visual range of the host to the fly which is determined by host size and environment. Vision appears to take precedence over olfaction when the host-seeking fly makes visual contact with the host. Landing and biting site choices appear to depend on a combination of visual and skin-associated chemical and thermal stimuli. Black fly responses to potential host stimuli seem dependent on the context in which the stimuli are received. Some stimuli (e.g. warmth) induce landing or biting for flies in the host seeking mode (or context) but induce escape reactions for non-host-seeking flies. Host choice (or rejection) may be based on the ability of these host stimuli, encountered in an appropriate sequence, to sustain the host seeking mode up to its consummation (blood feeding). Research on black fly host seeking has been slowed by the relative difficulty of doing meaningful behavioural experiments in the lab with this group, by the dearth of lab colonies and the difficulties and costs of maintaining them and by the lack of adequate field tools and experimental approaches.