Blood

see Circulatory System

University ofWales, Bangor

Of the 1 million described insect species, only 300 to 400 species feed on blood. The best known groups of bloodsucking insects are the lice, fleas, mosquitoes, sand flies, black flies, and bugs. But there are also several lesser known groups such as the nycteribiids and streblids, two families of cyclor-rhaphous flies found exclusively on bats; the Rhagionidae or snipe flies, a little-studied group of brachyceran flies; some lepidopterans (e.g., Calpe eustrigata); and even some coleop-terans (e.g., Platypsyllus castoris) that appear to have started on the evolutionary road to hematophagy.

Blood-sucking insects are of immense importance to humans, primarily because of the diseases they transmit. They also cause huge losses in animal husbandry because of disease transmission and because of direct losses linked to the pain and irritation they cause to animals. The most spectacular example of this agricultural loss is the prevention of the development of a cattle industry worth billions of dollars a year through much of sub-Saharan Africa because of tsetse fly-transmitted trypanosomiasis, although some argue that this has been Africa's savior because it has preserved wildlife and prevented desertification. Blood-sucking insects also cause serious losses in the tourist industry in areas as diparate as the French Camargue, the Scottish Highlands, and the state of Florida. We cannot ignore the sheer annoyance they can cause to us all.

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