Submitted by Kwiaht

No it’s not a bee or a wasp. It is a fly. To be precise it is Syrphus ribesii, a locally common species in the fly family known as the Syrphidae. Syrphid flies are often called “flower flies” on account of their frequently being seen visiting flowers to sip nectar and eat pollen like bees; or “hover flies” for the way they can hover almost motionless above a flower or the face of a nosey biologist. Syrphids are frequently mistaken for wasps, and sprayed or swatted, because they have evolved wasp-like color patterns and even buzzing to fool predators. In actuality Syrphids are timid and can neither sting nor bite. They flee at warp speed the moment a real wasp, bee or human approaches.

In popular culture, honeybees pollinate flowers. In the San Juan Islands, at least, wild bumblebees actually do most of the work in our wildflower meadows, gardens and orchards. Bumblebees are especially important on tiny, uninhabited islands, because they can fly a mile or farther over water, and as a result, maintain nests on larger islands while feeding on flowers on smaller ones. Smaller wild bees that make solitary nests, such as native miner and leafcutter bees, play a smaller role. They tend to nest close to their food and yield quickly to bumblebees. As a result, smaller bees tend than most of to pollinate flowers that bumblebees find unappetizing (such as Death Camas) or too small to bother visiting (like buttercups and native carrots).

Syrphids form a pollinator guild that also defers to bumblebees, and other bees as well. But Syrphids are very strong fliers, with more lift and maneuverability the bees or wasps. While bumblebees have an advantage in their imposing size and flight range—as well as their unusual ability to get a head start in the morning by “shivering” to warm up their flight muscles—they have difficulty flying in wet, windy conditions. Flies have the advantage in foul weather.

Syrphid flies can also afford to emerge early in spring when few flowers have yet bloomed, because their needs are few. A bumblebee queen, once she has emerged from her winter hibernation, must collect enough pollen and nectar to feed herself and a hive of daughters. Even small solitary bees build nests for a few eggs that they must provision as quickly as possible, while eating enough to continue flying. But Syrphids only eat pollen and nectar for flight energy, so they need less. They can also take longer breaks when the weather is foul, and keep laying eggs (and abandoning them) whenever they are active.

As a result of climate change, flies appear to play a growing role in pollinating the islands’ orchards and meadows. In 2016, flies outnumbered bees as spring flower visitors in the meadows, gardens and orchards that I have studied since 2010.

Many Syrphids lay their eggs where they find aphids. The larval flies emerge a few days later, feast on the aphids, and within just a week or two, metamorphose into adults. Other Syrphids lay their eggs in decomposing animal or vegetable material, like most flies. In the islands they like damp shrubby spots under roses or snowberries, for example. In either case, the adult Syrphid is only feeding herself, so she can manage with small numbers of flowers that contain relatively little pollen or nectar.

Some Syrphids also migrate northward over a period of weeks to months, taking advantage of the way that springtime conditions advance northward between the equinox and summer solstice. Adapted to cool, early spring conditions, these migratory flies form a pollinator vanguard that may never see summer as adults. Compared to Syrphids, bees are homebodies, tightly linked with floral resources close to their nests. As a result, bees are more vulnerable to local weather patterns and land use changes where they live.

As our Salish Sea climate change shifts towards warmer but stormier winter and spring weather, more of our wildflowers and orchard trees will flower before the weather settles, and few wildflowers will still be in flower by the time summer conditions prevail. It is likely that bees will grow more attached to gardens that flower in summer while flies provide more critical early spring pollinator services in wildflower meadows.

Fortunately the San Juan Islands have no shortage of Syrphids. Kwiaht pollinator studies have identified 33 species of Syrphids in the islands thus far, some of them very abundant and widespread, including several species that appear to have been introduced inadvertently from Europe, probably through the garden trade. There are several things a prudent farmer or gardener can do to attract and protect these useful flies. Leaving some shrubby ground undisturbed is one. Hedgerows and copses of trees are perfect especially is they are on low ground that stays wet in spring and early summer.

Another Syrphid-friendly practice is to avoid using pesticide or herbicide sprays on shrubby areas, on herbaceous plants to control aphids, or when flowers are blooming. Larval Syrphids are quite sensitive to these products, whether they are sprayed directly where they are feeding on aphids, or exposed to them in rain runoff on the ground. Like bees, adult Syrphids eat pollen and nectar and are poisoned by spray products that settle on flowers.

Getting to recognize and know our local Syrphids is also important. When you see an insect with white, yellow or orange markings on its “tail” (abdomen) take a closer look before you swat, spray or run. Look for big round fly eyes; the eyes of wasps and bees are small and oval. Check out the antennae. Flies have very short stubby antennae while bees and wasps have long narrow antennae that they use to touch and taste. If an insect has big saucer-like eyes and tiny antennae it’s not a wasp or bee, even if it buzzes loudly and flies threateningly close to you. It’s only pretending to be a wasp, when it actually is just about as useful to your garden as a bee—and cannot sting!