The Back-spotted Falsehorn (Temnostoma excentrica) is a large, yellow-and-black, Nearctic flower fly. A convincing Yellowjacket Wasp (Vespinae) mimic. In addition to being a visual mimic, this fly (and the other Falsehorns) lift and wave their black forefeet in front of their heads, imitating the antennae of wasps. Markings on thorax are whitish-gray in color. Paired yellow bands enclose a pair of black, rectangular spots on the 4th and 5th abdomen segments (open on segments 2 and 3). In the north, the abdominal markings can be white instead of yellow, mimicking the Bald-faced Hornet (Dolichovespula maculata).

Larvae found in decaying wood

Flight season: June

Similar species: Temnostoma alternans, Spilomyia alcimus, Spilomyia fusca, Somula decora, and Sphecomyia vittata, which are all yellowjacket mimics.

Flowers: Elderberry (Sambucus sp.)