Bee-impersonating flies have major pollinator potential, study finds

PULLMAN, Wash. — Syrphid flies, often called hover flies, appear as though they are a discount store version of bees. However, besides the distinctive yellow and black coloring, a new study finds these little flies are actually quite capable of being pollinators as well. Researchers from Washington State University say this discovery may prove useful to countless gardens and farms moving forward.

An observational study in Western Washington state discovered that, out of over 2,400 pollinator visits to various flowers on urban and rural farms, about 35 percent of those treks were made by flies not bees. The vast majority of those flies were black and yellow striped syrphid flies. For certain plants, such as peas, kale, and lilies, these flies appear to be the only source of pollination. To be fair to all the bee lovers out there, bees still made up the majority of floral pollination visits (61%).

“We found that there really were a dramatic number of pollinators visiting flowers that were not bees,” says lead study author Rae Olsson, a WSU post-doctoral fellow, in a university release. “The majority of the non-bee pollinators were flies, and most of those were syrphid flies which is a group that commonly mimics bees.”

Pollinating may be a bee’s work, but others can do it too

The syrphid fly’s striking resemblance to bees no doubt helps it avoid various predators, but make no mistake these insects are flies not bees. Syrphid flies only have two wings. All bees boast four wings.

Moreover, these flies also offer additional benefits for the flowers they pollinate. Study authors explain young syrphid flies routinely eat tiny insect pests like aphids. Then, by the time they mature into adults, the flies eat nectar and visit flowers, thus moving pollen from point A to point B just like bees. Notably, the flies don’t intentionally pollinate like bees, who gather pollen to feed their offspring.

Researchers analyzed various plants and pollinating insects and spiders on 19 rural farms and 17 urban farms and gardens along the Interstate 5 corridor in Western Washington. The team carried out surveys on six occasions over the span of two years. Besides just bees and flies, scientists also took note of all other visitors including wasps, spiders, lacewings, butterflies, dragonflies, beetles, and ants. However, these arthropods only made up roughly four percent of observed interactions.

In summation, study authors believe their work indicates farmers, gardeners, and scientists should start focusing on alternative pollinators more thoroughly.

Bee populations are declining, and we are trying to help them, but there’s room at the table for all the pollinators,” Olsson explains. “There are a lot of conservation and monitoring efforts for bees, but that doesn’t extend to some of the other pollinators. I think people will be surprised to find that there are a lot more different types of pollinating insects – all we really need to do is to start paying a little more attention to them.”

How can you help the pollinating process all year long?

Study authors also noted pollinator differences among urban and rural areas. Urban areas appear to experience a more diverse array of pollinators. Rural farms, though, had a greater overall number of pollinators.

If any farmer or gardener is looking to increase the number and or diversity of pollinators on their land, researchers suggest planting numerous different plants and flowers. Plants that flower all season long are also advantageous, because various pollinators adhere to different life stages at dissimilar times of the year.

“Some pollinators like certain butterflies and moths are only present in a pollinating form for a small period of time,” Olsson concludes. “They may only live for a few days as adults, so when they emerge and are ready to pollinate, it’s good to make sure that you have something for them to eat.”

The study appears in the journal Food Webs.