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a genus of argasid ticks (Argasidae). The elongated, flattened body is capable of greatly increasing in size during bloodsucking owing to its elastic folded covering. There are about 40 species, distributed mainly in the tropics and sub-tropics. Seven species are found in the USSR, in Middle Asia, Kazakhstan, the Crimea, Moldavia, and the Caucasus. The ticks live in the burrows, nests, and temporary shelters of mammals, birds, and reptiles. They feed on the blood of these animals. O. papillipes, which is found in Middle Asia, and O. verrucosus, which is found in the Caucasus, are carriers of the causative agents of relapsing fever in man.