Female Black-Tailed Bee Flies lay their fertilized eggs in the ground nests of certain solitary bee species. The Black-Tailed Bee Fly larvae hatch and eat the larvae of the resident bees, making them parasites. Once they eat the competition, they go on to eat any food stores left by their mother. They will then pupate in that nest and eventually emerge as adults in the summer.
This species is most active in the summer on sunny days. They can be found in open fields, back yards and park, either resting on plants or buzzing over blossoms. They are able to hover over the flowers they drink from, much like a hummingbird. Males will often hover over flowers while waiting for a female to pass by. Males then dart after the female in the hope of mating with her. While observers can get close, the Black-Tailed Bee Fly is quite aware of its surroundings and can bolt away so quickly, they are difficult to catch.