Bee flies can be found throughout southern Canada and the U.S. The adults visit flowers for nectar. The Larva are parasites to some insect larvae such as ants, beetles, bees, caterpillars, or wasps. There are 43 different species of Exoprosopa Bee Flies within North America. Most are found in arid regions, they nectar on flowers, and prefer aster varieties of plants. Here is one on a Pineywoods Geranium in northern Arizona last summer.