Ragweed (Ambrosia artemisiifolia) is a native plant that is just beginning to flower now. It is an inconspicuous plant but it can cause grief for those allergic to it. It often grows with goldenrod (Solidago), and people mistakenly think goldenrod is the culprit for their allergies. These little flies are good guys. The adults lay eggs on the plant and the larvae develop in the ragweed seeds. These are beneficial insects, exerting some control on the plant. Although ragweed is abundant, it is likely it would be far more so without these guys. There are also other insects that feed on ragweed, including a moth caterpillar and a leaf-eating beetle.

These flies are perhaps 2-4 mm in size. As well, these are NOT the tiny black flies that cluster around fruit in our homes. NO RELATION!