By Julie Reiff
Documenting the insects who visited the Habitat For All Garden last summer was intimidating at first. I could tell a honeybee from a bumble bee but not much more. Increasingly, I photographed insects that looked like bees or wasps…but were clearly different, too. Thanks to the iNaturalist app, I learned about hoverflies…our most important pollinators after bees.
Hoverflies, also called flower flies or syrphid flies, are members of the fly family (Diptera). Like all flies, they have big eyes and two wings–not four like bees. (The term Diptera actually comes from the Greek for “two wings.”) They also have short, stubby antennae and differ from other flies by a false vein in their wing.
Because of their short, unspecialized mouthparts, they prefer to visit flat, open flowers or clusters of small flowers where they can perch on the petals. And because they’re around throughout the growing season, Syrphids need a variety of blossoms that bloom over a long range of time. I have found them on chickweed, evening primrose, Mexican sunflowers, and even resting on our garden signs.
hoverflies are our most important pollinators after bees.
What makes hoverflies so interesting is that they have adapted to mimic the color patterns of wasps and bees, presumably to gain protection from predators. Unlike wasps and bees, though, these flies are incapable of stinging and are totally harmless. Adults feed mainly on nectar and pollen; females need this food to produce viable eggs.
Adult hoverflies are important pollinators, but in the larval stage they are equally important to agriculture. When larvae (fly larvae are called maggots) hatch from the eggs, some species prey on aphids and other plant-sucking insects. An individual may consume as many as 400 aphids before it pupates. Other species of hoverfly eat decaying plant and animal matter, which serves an important garden function as well.
There are more than 6,000 species of Syrphidae around the world, and Maine hosts more than 100. We documented 15 different species in the Habitat For All Garden last season:
Maize calligrapher (Toxomerus politus)
Eastern calligrapher (Toxomerus geminates)
Margined calligrapher (Toxomerus marginatus)
Transverse-banded flower fly (Eristalis transversa)
Compost fly (Syritta pippins)
Globetails (Genus Sphaerophoria)
Bald-faced hornet fly (Spilomyia fascia)
Black-shouldered drone fly (Eristalis dmidiata)
Common drone fly (Eristalis tenax)
Black-spotted falsehorn (Temnostoma excentrica)
American snout fly (Rhingia nasica)
Sedgesitters (Genus Platycheirus)
American whitebelt (Leucozona americana)
Hairy-eyed mimic fly (Mallota posticata)
Yellow-margined marsh fly (Helophilus lapponicus)
Like some bees, hoverflies overwinter in protected locations, like leaf piles or brush—most likely as pupae here in Maine and other cold locations. So, as for bees, it’s a good idea to leave your leaves and garden debris alone for a bit in the spring until these insects have had a chance to wake up. Five Days Above Fifty is a good mantra for insect-friendly gardening. And remember to plant a variety of blooms that will last all season…or let a few wildflowers grow somewhere in your yard. These blooms might be exactly what these hoverflies are looking for.
Next month we’ll dig still deeper into who our garden visitors were at Valentine Farm and explore more ways we can make our landscapes inviting places for these very productive yet tiny creatures. We'll also be talking more about how to use iNaturalist and how you can join us in the Habitat For All Garden next summer.
Julie Reiff is a newly minted Maine Master Naturalist and a volunteer in the Habitat For All Garden at Valentine Farm. She coordinates the garden's pollinator project on iNaturalist.
Sources: