Discovering Diptera

I find it refreshing to take my time to slow down in a garden, meadow, or forest. Then I can watch closely for birds and insects. This summer I’ve been standing still and crouching down with my camera to discover the scientific order of insects called Diptera, Greek for “two” and “wings,” or the animals we know as flies.

Top photo: A Western Pond Fly (Sericomyia chalcopyga) pollinating Western Sweet Coltsfoot in Cappy’s forest.

Greenbottle Fly (Genus Lucilia)

Our native flies (don’t worry, I’m not going to write about pesky house flies) can be incredibly beautiful, and are very important pollinators for native plants, garden plants, and agriculture. I wrote in Rainshadow Journal a few years ago about insects on the Olympic Peninsula, including a few flies: rainshadownorthwest.com/2021/09/04/insects-on-the-peninsula-part-2/. Now we’ll look at some more wonderful and beneficial fly species. This is a Greenbottle Fly (Genus Lucilia) pollinating a Nootka Rose. When I posted it on iNaturalist, a biodiversity citizen science site, the collections assistant at Harvard’s Museum of Comparative Zoology, and creator of the project, Flies of the US and Canada, wrote, “We can narrow this down to one of the following species: Lucilia sericata, Lucilia thatuna.” He noted this was a female. (Experts helping is one reason I love iNaturalist!)

Greater Bee Fly (Genus Bombylius)

To find a Bee Fly is special. I’m not sure of the species of this elegant bee fly on Hurricane Hill in the Olympics. Though it’s small, it’s a Greater Bee Fly in the Genus Bombylius. An undergraduate student at Cornell University, who is interested in flies, particularly the Bombyliidae, took a look at my photos on iNaturalist. In this case it was impossible to determine the species just with photos. This Bee Fly is pollinating Mountain Sandwort with its long, stiff, non-retractable  proboscis that’s almost as long as its entire body. I’ve found Greater Bee Flies at sea level, too, such as one pollinating a daisy in Ft. Worden, I had to sneak up slowly on this insect to snap a quick photo with my macro lens.

Small-headed Fly (Eulonchus sapphirinus)

Another fly with an elongated proboscis is the Small-headed Fly (Eulonchus sapphirinus). Notice how this one uses its front legs to steady its proboscis. I love the iridescent teal color of its abdomen, and the pollen sprinkled over it. Most people aren’t familiar with the rare Small-headed Flies. They have a humpback, a very round head with huge eyes, and they hold their wings against the sides of their abdomen when resting. A few years ago I planted a native Mock Orange shrub in our garden, and in July when it blooms, I stand alongside with my macro lens to capture close-ups of butterflies, bees, and flies. Per the WSU Extension: “A garden with a good diversity of local native flora in and around back yards, will improve the abundance and diversity of local, beneficial arthropods. Native flora also provides natural overwintering sites for many beneficial insects and it is useful to leave at least a small area of native vegetation undisturbed during fall and winter.”

Seaweed Flies (Genus Fucellia)

When you walk along our local beaches with seaweed washed ashore, you’ll notice swarms of Seaweed Flies (Genus Fucellia). In this photo Seaweed Flies of different sizes are crawling on kelp, and I’ve also seen them feeding inside empty crab carapaces. They have huge red eyes, a striped brown and pale blue thorax, and iridescent wings. It’s difficult to find any information at all about them. Even Merrill A. Peterson, in his excellent field guide, Pacific Northwest Insects, notes that there are 4,000 fly species in the Pacific Northwest, but he doesn’t mention our very common local residents. All I could learn online is that there are 19 Fucellia species, with “several” along the Pacific beaches. When Barn Swallows swoop low over Port Townsend beaches to grab insects in flight, are they feeding on Seaweed Flies?

Large Crane Fly (Phoroctenia vittata)

This is a Large Crane Fly (Phoroctenia vittata) caught by a Pacific Wren who struggled with such a big mouthful. Crane flies have very long, spindly legs and wings. Merrill A. Peterson writes: “Crane flies vary in size from tiny to massive… This is the most diverse fly family, with over 15,000 known species.” Ornithologists have determined that 60% of bird species depend on insects as their primary food source. Even seed-eating birds often feed soft caterpillars and other insects to their nestlings.

Common Lagoon Fly (Eristalinus aeneus)

Many of the flies I find locally are in the Syrphidae Family, commonly known as Hover Flies or Flower Flies. They are usually small, they hover like a helicopter, and sometimes have large and magnificent eyes. My favorite fly eyes are the green polka-dotted eyes of the Common Lagoon Fly (Eristalinus aeneus). These flies pollinate flowers close to water. This one, covered in pollen on an Ox-eye Daisy, was near Chinese Gardens Lagoon. Naturalist David Lukas writes in his blog “Hovering Among Us” on lukasguides.com: “Hoverflies are now known to be the second most important pollinators in the world after bees, pollinating over 70% of all global food crops and over 70% of all animal-pollinated wildflowers.”

Common Drone Fly (Eristalis tenax)

Another local Hover Fly group are the Drone Flies, not named for modern drone technology, but for their similarity in appearance to male European Honey Bees, called “drones.” The most widely distributed of all Hover Flies is the Common Drone Fly (Eristalis tenax). This fly is a bee “mimic,” but unlike a bee, its huge eyes practically touch, and its hindlegs don’t carry pollen sacs. I’ve mostly found them in late summer, like this one pollinating a Common California Aster on Indian Island.

Black-footed Drone Fly (Eristalis hirta)

A Black-footed Drone Fly (Eristalis hirta) doesn’t look much like a honey bee. To identify this insect, look for the pale stripes on its abdomen, orange triangles near the thorax, and fuzzy setae all over. This one was on Puget Sound Gumweed, one of my favorite local wildflowers because it attracts such an assortment of insects. While pollination is so important to plants and people, flowers provide the insects with what they need, too— nectar for energy and pollen for protein.

Margined Calligrapher (Toxomerus marginatus)

Our last Hover Fly is a Margined Calligrapher (Toxomerus marginatus). At first glance you may think it’s a wasp, because Calligrapher Flies mimic wasps, though the patterns on their abdomens are much prettier. Calligrapher Flies have enormous eyes in shades of red to black that dominate their heads. This one was pollinating pink yarrow in our garden on a late summer day. Since this is the only one I’ve ever seen, it was a surprise to realize this is the “Most Observed Species” on the iNaturalist project, Flies of the US and Canada, because its range encompasses most of North America. Port Townsend Entomologist Richard Lewis encourages everyone to become involved in a citizen science project that helps identify insects such as iNaturalist, The Great Sunflower for pollinators, Bumble Bee Watch just for bumble bees and eButterfly for butterflies. Also he recommends BugGuide as a good place to look for ID assistance. Richard says, “One of the big problems with insect decline is that we don’t have any kind of baseline information on how many bugs are out there or what types of bugs are out there.” I hope you will consider joining one, too.