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Biting Midges as Pests

Anyone with any significant outdoor experience knows that biting midges can be terribly annoying. They may occur in huge numbers (often just 1 or 2 species) in places where there is appropriate and abundant habitat and their bite (sometimes unnoticed at the time) can produce burning and itching welts completely out of proportion to their small size. As in virtually all other families of biting flies, only the females bite (they need the blood to develop their eggs). The culprits are restricted to four of the 108 genera known worldwide but they are most diverse in two genera: species of the genus of Leptoconops, with 155 species and those of Culicoides, with over 1,360 species.

Members of Leptoconops all breed in beach sand or alkaline soils. Generally the species are restricted to marine beaches or at least salty habitats (as those living near Great Salt Lake, Utah, USA know) and the adults tend to be daytime biters, generally on the lower legs (or the whole body if one is sitting or lying down). The females have a remarkable behaviour in which they bury themselves just under the sand surface when they are resting. Some species transmit filarial worms in humans and donkeys.

Adult Culicoides occur, in varying numbers, in virtually every region of the world (not New Zealand), from the coast to the highest elevations. Despite the large number of species known, only a small percentage feed on humans. For example, in Costa Rica, with at least 150 species, only Culicoides furensC. phlebotomusC. pseudodiabolicus, and C. paraensis occur in large enough numbers to be considered serious pests of humans. In particular, the well named C. furens (furious or rages, in Latin), common near mangrove swamps, may occur in large numbers in from Florida and Texas in the USA south to Ecuador and Brazil and make life in some coastal areas a living hell!

Some other species feed on domestic animals. Many, feed on a variety of fowl, cattle, horses and others. In large measure, we do not know what the other species of Culicoides feed on, although it is virtually certain that their hosts are other vertebrates (other than a very few that feed on mosquitoes and sandflies in Asia).

There are at least 82 viruses, 48 protozoa and 26 species of filarial worms that are present in various species of Ceratopogonidae (nearly all of these are species of Culicoides). Some of these are serious pests of humans and domestic animals, including Oropouche virus in humans in Central and South America, African horse sickness in southern Europe, Africa and Asia, Bluetongue virus in ungulates nearly worldwide and Epizootic Haemorrhagic Disease in at least deer and antelopes in North America, Japan, Africa, Australia.  Many of the protozoa are found in birds (but also in various mammals) and filarial worms are present in humans, various other mammals and birds.

Considering the number of diseases of other vertebrates vectored by species of Culicoides in the better studied regions, it is almost certain that some diseases of non-economic vertebrates are transmitted by other species of Culicoides. Very little research, however, has been done on the vast majority of mammal and bird wildlife species.