BugBytes: There’s more to flies than meets the eye


Marian Lyman Kirst

This soldier fly—probably Odontomyia cincta—was captured near a stagnant channel of the Yellowstone River near Billings. Look for them on flowers this summer. (Note: This fly was alive and quite active when photographed.)

For most Montanans, flies probably fall into two groups: 1) Things you swat, often with lunatic gusto and 2) Things you cast, often (in my case) with lunatic glee.

And if asked to visualize a “fly,” most people probably picture something that resembles the familiar, if drab, house and cluster flies that shelter—or become trapped—in homes. Or, perhaps, they envisage the metallic bluebottles that amass in droning clouds around garbage cans and dog poop.

(By the way, an excellent, if seldom used, collective noun for a group of flies is a “business.” So, now you can say things like, “Hey! Look at that business of flies getting down to business on Fido’s business,” and feel awesome about yourself.)

Deer fly

Marian Lyman Kirst

This deer fly, found recently near Cooke City, exhibits the hypnotizing eye markings common to most members of Chrysopinae, the subfamily of flies to which all deer flies belong.

Flies belong to the insect order Diptera (meaning “two-winged”), a massive group that contains more than 150,000 known species. Flies vary mightily in size, shape, color, feeding strategy and development. Some, like long-legged flies (family Dolichopodidae), are simply gorgeous. If you have grapes, sunflowers or Virginia creeper in your yard, you’ve almost certainly seen the burnished green beauties tracing around the leaves looking for prey and mates.

Others, such as the bee fly Bombylius major, are achingly cute, resembling creatures Jim Henson might have devised if all he’d had to work with was a fly, a mouse and a pool cue.

And, yes, dipterans also include some fantastically annoying members like the deer fly and even potentially deadly ones like the West Nile and malaria-vectoring mosquito. But even these pests, only the females of which bite, have some interesting aspects.

Deer flies, for example, are famous for their psychedelic peepers, the colors of which are created via corneal layering. The function of these ocular patterns is not crystal clear but studies suggest they filter light in ways that may aid the flies in courtship and prey targeting.

The mosquito, meanwhile, recently served as muse to Japanese scientists, who used the insect’s proboscis as a model in the creation of a motorized needle that delivers virtually pain-free injections.

Montana also has some dipterans that are, dare I say it, super fly.

A couple of weeks ago, while walking our dog near the river, my husband and I ran across a “baller” species of soldier fly (family Stratiomyidae) sitting atop a yellow aster. Its color—a limey, matte green shade I’ve only ever seen on fingernails and pimped-out Challenger SRTs (Dodge calls the hue “sublime green”)—caught my attention.

Bereft of collecting jars, and having used our lone dog bag for other business, I was forced to “Gandalf” the fly for deposition into my purse. The insect was subsequently transferred to a Sweetheart bakery sack that we snatched from the bushes. “Gandalfing,” by the way, is a term I use to describe the catching of an insect in the palm of your hand without damaging it. For a visual, refer to this scene from the Two Towers. Welcome to Nerdsville, friends.

Anyway, soldier flies get their common name from their bold, brassy markings, which are thought to resemble those used in military regalia. Do not, though, be unnerved by the insect’s aggressive-sounding handle. Solider flies are harmless, nectar-sipping pretenders.

Their wasp-like striping and vaguely menacing “buzz” are examples of Batesian mimicry, a passive defensive strategy in which tasty or unarmed insects avoid being eaten thanks to their resemblance to distasteful or harmful ones.


Elley Swan

This illustration, by local artist and painter Elley Swan, depicts a soldier fly larvae from the genus Odontomyia “butt breathing” at sunset.

But if you’re not sure whether you’re looking at a wasp, a bee, or a soldier fly, check out the insect’s wings (of which flies only have one pair) and antennae. Soldier fly wings fold, like pruning shears, over their backs and their antennae are often aligned in a T or Y shape.

Soldier fly larvae, meanwhile, are tiny, worm-like creatures found under bark, in water, soil and dung, and even in ant nests. That we found our adult near a stagnant river channel makes sense considering the larvae of this particular soldier fly (from the subfamily Stratiomyinae) are aquatic.

The tiny, flattened torpedoes are equipped in the rear with a brush of hairs that allow the insects to float, upside down, at the water’s surface where they get oxygen. The larvae feast on algae, organic matter and microorganisms and, thanks to calcium carbonate-infused exoskeletons, are remarkably tolerant to drought, high salinity and pollution.

You’re probably more likely to run across and recognize the soldier fly adults than the larvae when out and about this summer. But keep an eye out for both of them and let us know what you find! Oh, and if you want some “Gandalfing” practice, try it out on the bits of cotton floating around. You’ll get wizard-good in no time.

The nitty gritty:

Common name: Soldier fly 

Taxonomic order: Diptera

Where to look: You can find adults on flowers and shrubs in fields and woodlands and the larvae in soil, compost, dung and slow-running or stagnant water.

Hot spot: A likely location in which to spot soldier flies in our area is on flowers near channels and offshoots of the Yellowstone River.

When to look: May through July.

Marian Lyman KirstM.L. Kirst is a Billings-based, bug-obsessed freelance writer and photographer with a background in environmental studies and science journalism, and she is currently working on a degree in entomology. Her work tends to focus on natural history and wildlife conservation. But her prime directive is to blend art, science and writing in a way that inspires others to celebrate the beauty, ingenuity, and diversity of insects, spiders and their kin.




         Bonus photograph:


Nickolas Olson

This gorgeous shot of a flesh fly (family Sarcophagidae) is our first reader-contributed photo and was taken by local photographer Nickolas Olson. Nick spotted the fly on the patio at Carter’s Brewing. (Gotta love a guy who takes time away from his micro brew to snap a bug pic.) Most flesh fly larvae feed on and develop in small carrion or are parasites and predators of other small arthropods. A few species, though, develop in larger—including human—corpses and, thus, can be of great importance in forensic cases. The adults, however, feed chiefly on sugar-rich substances like nectar, sap and fruit juices, which may explain this fly’s hankering for a Carter’s pit stop.

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