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a genus of flies of the family Syrphidae. The ordinary drone fly (E. tenax) is approximately 1.5 cm long; in coloring it resembles the domestic bee. Members of Eristalis are widely distributed and are found on flowers all summer long. The larvae of Eristalis, the rat-tailed maggots, have a cylindrical body; the body ends with a respiratory tube consisting of elbows that move apart (they can elongate up to 15 cm). The rat-tailed larvae inhabit drainage ditches, shallow bodies of water with putrefying slime, and similar places. They use the respiratory tube to breath atmospheric air, which enables them to inhabit oxygen-poor water. The presence of rat-tailed larvae is an index of water pollution. The larva pupates on shore.