Adult flies in the Syrphidae family are conspicuous day-flying insects that are very skilled at hovering, and love to frequent flowers, which led to their common names of “hover flies” or “flower flies”. They are brightly colored and are very abundant in many familiar environments. Many of the hover flies strongly mimic bees in coloration and sound and it is no wonder why many folks confuse them for being small bees or even pests. Many folks think they are “sweat bees”. Like bees, they are significant pollinators. However, these flies neither sting nor produce honey. Some of the flies in this family mimic wasps, such as bald-faced hornets or yellowjackets, in appearance, sound and behavior. However, flies have only one pair of wings, unlike bees and wasps which have two pair of wings.
Most flower fly larvae, including those yellow and black species often found in gardens, are predators of aphids and other soft-bodied insects so they are actually quite beneficial. They move along the plant surfaces searching for prey. A syrphid fly larva may consume up to 400 aphids during its development. Most adult hover flies feed on nectar but some will feed upon alternative sugar sources. The “honeydew” excrement produced by aphids can be a major food source for hover flies. The presence of aphids and honeydew is one reason we are seeing many hover flies in sorghum. These insects are not pests, so please do not make an insecticide application for them.
Cornell University: http://www.biocontrol.entomology.cornell.edu/predators/syrphids.php
Marshall, S. A. 2006. Insects: Their Natural History and Diversity. Firefly Books Ltd. Buffalo, NY 14205. Pgs. 403 – 404.