(Photos and story by Anita Fernandez)
The word “fly” probably elicits feelings of annoyance in most of us and the word “hornet” may bring up trepidation and fear. After all, those of us who have interacted directly with hornets, know they can be aggressive and are known to sting. The insect on the left is a Bald-faced Hornet and the one on the right is a Bald-faced Hornet Fly. The Bald-faced Hornet is a social species of wasp, constructing paper nests to house their large colonies. However, if you do not attempt to handle it or its nest and maintain a respectful distance (this photo was taken at a distance of about two feet), these wasps are generally much more interested in foraging for food than using up energy attacking you. They harvest nectar and pollen from flowering plants but capture insects (caterpillars and aphids are common food sources) and spiders to chew up and feed their young. It is not a true “hornet” at all, but a member of the native North American yellowjackets.
The Bald-faced Hornet Fly is a syrphid fly, commonly referred to as a flower fly because they feed on nectar as adults, or a hover fly because of their ability to hold still in flight. They, like the Bald-faced Hornet, are pollinators and their larvae also help eradicate aphid pests from gardens. However, unlike the wasp species, the Bald-Faced Hornet Fly does not create a paper wasp or nest colonially, meaning that it is less aggressive. Also, although the fly mimics the wasp, they are unable to sting like a wasp.
A key difference in their identification is in the eyes. Both are white and black, but the eyes of the Bald-faced Hornet are elongated and curved, whereas the eyes of the Bald-faced Hornet Fly are more rounded and set close together. Another distinguishing feature is that flies have only two wings, or one set, whereas wasps have four total wings, or two sets. This can be a difficult feature to determine on these often-moving insects, especially during flight.