Bloodsucking Flies

a large and varied complex of two-winged insects of the order Diptera that suck the blood of man and other warm-blooded animals. The group includes mosquitoes, gnats, midges, and horseflies, as well as a number of bloodsucking flies (autumn stableflies and cow flies, for example) and in the south, sand flies. Bloodsucking flies are ubiquitous except for the arctic islands and the antarctic. Their development and mass reproduction are connected with standing and flowing water, with marshy areas, and with high groundwater levels. The sites of constant mass reproduction in most cases are found in uninhabited or sparsely inhabited places. In the USSR, these are primarily in the tundra, the forest tundra, and the taiga. In the forested steppes, particularly in the steppes, in semiarid lands, and in deserts, mass development of bloodsucking flies is confined to the floodplains and deltas of great rivers and the shore areas of lakes, usually highly saline lakes.

The absolute numbers of bloodsucking flies in areas of their mass reproduction can be extremely great. Cattle, horses, deer, and other animals attract them to a significantly greater degree than does man. The apparent composition of a group of bloodsuckers is usually one species (or several). In the north in the lower reaches of the Pechora River, of the ten types of attacking mosquitoes, Aëdes punctor sharply predominates. In the course of the season, a change is observed in the dominant groups and species of bloodsucking flies. In the deciduous forests of the Far East, biting midges attack first, followed by aëdes mosquitoes, and then horseflies; by midsummer the midges disappear, but the number of mosquitoes increases, of genera Culex and Anopheles, and mass types of horseflies gradually replace each other. Aëdes mosquitoes do not appear simultaneously in the spring, but in three successive waves, called respectively early-, mid-, and late-spring types.

The economic loss caused by bloodsucking flies is great and varied. Human labor productivity during periods of mass activity by these insects is greatly reduced, and the number of occupational accidents increases; the pests interfere with normal relaxation and sleep. The saliva of the insects deposited under the skin upon puncture is poisonous and causes burning and itching at the puncture site, and at times inflammation and swelling. Animals subjected to attacks cease grazing and are in constant movement, gathering in thickets or in the water. As a result they lose weight, and milk production decreases.

Many forms of bloodsucking flies are mechanical and specific carriers of human and animal pathogenes—for example, Siberian malignant anthrax, glanders, and infectious equine anemia. Mosquitoes are the specific carriers of malaria of birds and man, Japanese encephalitis, encephalomyelitis in horses, anaplasmosis in cattle, rabbit fever, and other diseases. Gnats carry onchocerciasis in cattle and parasitic blood infections in domestic fowl. Midges transmit onchocerciasis, African horse plague, and Japanese encephalitis. Horseflies carry trypanosomiasis in camels and horses. Sand flies transmit leishmaniosis and mosquito-fever pathogenes.

The biological diversity of individual groups of these insects greatly complicates the struggle against them as an entity. General countermeasures against the larvae are a practical impossibility. Nonspecific measures and prophylaxis are of chief significance. Planned territorial reclamation reduces the numbers of individual groups or entire complexes of bloodsucking insects. Thus, as a result of selective cutting in deciduous forests of the Far East, the forest humus floor dried and the numbers of midges diminished sharply. Water supply regulation in rivers, and particularly construction of hydroelectric stations, leads to significant reductions in the gnat population. Ground drainage and other drying and improvement projects allow reduction of mosquito, horsefly, and midge populations. Individual protection of man and agricultural animals can be achieved by repellents, which ward off most groups and species of bloodsucking flies. The best of these are diethyltoluamide (DETA) and benzimide. Mechanical protection from these insects is possible in buildings with window and door screens and with vestibules. Flying bloodsuckers can be destroyed outdoors and in buildings with the aid of poisonous smoke and mist.