A non-native muscid hunter fly, Coenosia attenuata Stein, was first discovered in the U.S. in 2002 by an IPM scout in a greenhouse near Syracuse, NY. Native to southern Europe, this fly has recently been found in greenhouses across North and South America, northern and southern Europe, and the Middle East. It has spread and become established in greenhouses unintentionally. Both adults and larvae are obligate generalist predators. Adults are aerial predators of flying prey, and larvae are soil dwelling predators. Predation rate, reproduction, and survivorship of C. attenuata adults and larvae were high on the greenhouses pests Bradysia impatiens (Diptera: Sciaridae) or Scatella tenuicosta (Diptera: Ephydridae), but on adult Bemisia argentifolii (Hemiptera: Alyrodidae), adult predation was low and adult survival and reproduction was not different than that of unfed controls. Because C. attenuata is a generalist predator, adult and larval predation of some non-target species was evaluated.