In addition to mosquitoes, the District also controls black flies which can be a nuisance for farmers and ranchers. They bite livestock, especially around eyes, ears and reproductive organs. Like mosquitoes, black fly life begins in water. They however prefer flowing water (whereas mosquitoes need stagnant water) and can be found in canals, ditches, and the Jordan River. They fly erratically and in swarms and are NOT your typical picnic fly.