Swat one fly on a North Dakota porch and there’s a good chance another dozen species are going unnoticed just a few feet away. The types of flies in North Dakota range from painful biters that chase down livestock to hairy mimics so convincing they can fool a beekeeper at a glance. Beyond the common housefly, the state’s grasslands, river bottoms, and wetlands support predators, pollinators, and decomposers that quietly keep local food webs running.
Three species stand out for how differently they look, hunt, and interact with people spending time outdoors: the ring-clawed deer fly, the bee-like robber fly, and the picture-winged fly. Each one tells a slightly different story about how flies survive on the northern prairie.
| Fly | Family | Typical Size | Notable Trait |
|---|---|---|---|
| Ring-Clawed Deer Fly | Tabanidae | Medium-sized biting fly | Slicing bite from blood-feeding females |
| Bee-Like Robber Fly | Asilidae | 15–25 mm | Bumblebee mimicry with ambush hunting |
| Picture-Winged Fly | Ulidiidae | A few millimeters | Patterned wings used for signaling |
1. The Ring-Clawed Deer Fly: A Familiar Biter Among Flies in North Dakota
The ring-clawed deer fly, known scientifically as Chrysops cincticornis, belongs to a genus that field guides sometimes list under a slightly different common name. iNaturalist records the species under the name Ring-clawed Deer Fly, distinguishing it from dozens of other Chrysops species tracked across North America. Ring-clawed Deer Fly Chrysops cincticornis is one of many species cataloged within the genus alongside relatives like the Bothersome Deer Fly and Colorado Deer Fly.
Like every other species in its genus, this fly sits within a well-documented insect family. Chrysops species are classified as deer flies in the family Tabanidae, the same family that includes horse flies. That family connection matters for identification purposes, since Tabanidae species share a similar body plan: stout, broad-headed flies with large eyes and wings that often carry dark patterning.
Females are the ones people notice most, since they need a blood meal to develop eggs and use scissor-like mouthparts to slice skin rather than pierce it cleanly. Males, by contrast, typically feed on nectar and pollen and rarely bother people at all. Deer flies tend to be most active on warm, still days near wooded edges, wetlands, and pastures, where livestock and pets are frequent targets alongside hikers and anglers.
Pro Tip: Deer flies key in on movement and dark colors, so lighter-colored clothing and staying away from wooded shade during peak midday activity can reduce the number of bites received outdoors.
Because these flies bother animals as much as people, anyone dealing with recurring bites on a dog or livestock might find it useful to compare notes on common types of flies that target dogs. Deer flies also show up in a different context entirely: their bulky, banded silhouette has inspired more than a few patterns among flies tied for fishing, where anglers imitate biting insects that trout are already used to snapping at.
2. The Bee-Like Robber Fly
Few flies pull off disguise as well as the bee-like robber fly. Members of the genus Laphria are known as bee-like robber flies, and the resemblance is not accidental. These large flies measure 15 to 25 millimeters in length, and most species are quite hairy and black in color, with some carrying bee-mimicking markings of black and yellow stripes and pollen hairs.
The mimicry goes beyond looks. According to a Wikipedia summary of the genus, Laphria species prey on a variety of insects, including other robber flies, bees, wasps, and beetles, using a proboscis to penetrate prey and inject enzymes that dissolve the tissue inside. That hunting style puts them in the same category as many other Asilidae, a family built almost entirely around ambush predation.
Spotting the difference between a robber fly and an actual bumblebee takes a closer look. A quick look at the antennae shows they are short, while bees have longer antennae that are bent or elbowed, and the brown wings flap rapidly enough to create an audible buzzing sound in flight. Texas A&M’s field guide to common insects adds a simpler rule of thumb: true flies have only one pair of wings, which readily separates robber flies from the bees they resemble.
Behavior offers another clue. Researchers who track the genus note that Laphria species show more direct, purposeful flight patterns than the slower, erratic flight of actual bumble bees, and they may be observed perching on flowers without feeding, a habit real bees rarely display. The same source points out that the genus is distributed across North America and parts of Europe, which helps explain why bee-like robber flies show up across such a wide range of prairie and woodland habitats.
Their life cycle is just as predatory as their adult hunting style. Larvae are parasitic on immature stages of other insects, including beetles, flies, wasps, moths, and grasshoppers, hatching into slender, shiny, white, legless larvae that develop through several stages before pupating. The full life cycle usually takes more than one year to complete. Adults keep the predatory theme going, since they have piercing-sucking mouthparts and are generally considered beneficial insects, though handling one improperly can result in a painful bite.
Anyone comparing painful insect encounters across the region might also want to check the broader list of venomous animals in North Dakota, though it’s worth noting a robber fly’s bite is defensive rather than venomous in the medical sense. Similar bee-mimicking robber flies elsewhere in the genus are distinguished from look-alikes by antennae thickness, since Laphria can be told apart from other bumble bee-mimicking robber flies by their thick antennae, while the related genus Mallophora has thin terminal antennal segments and generally hairier bodies.
3. The Picture-Winged Fly
Picture-winged flies belong to the family Ulidiidae, a group named for the patterned, often smoky or banded markings that decorate their wings. Unlike deer flies or robber flies, these insects rarely bite or hunt other insects. Most species spend their larval stage breaking down decaying plant material, stems, or fruit, making them part of the same decomposer community that helps recycle organic matter across prairie habitats.
One of the more distinctive behaviors in this family is wing-waving, a display many species use to signal territory or ward off rivals by flicking their patterned wings in a slow, deliberate motion. Some researchers have suggested this movement mimics the posturing of jumping spiders, a possible strategy for deterring predators that would otherwise treat a small fly as an easy meal.
Important Note: Detailed, species-level records for picture-winged flies specific to North Dakota are limited compared to better-studied groups like deer flies and robber flies. The behaviors and traits described here reflect general characteristics of the Ulidiidae family rather than confirmed observations of a single named species in the state.
Even without a complete regional catalog, picture-winged flies fit into the same broader story as the state’s other insects: small, often overlooked species that contribute to pollination, decomposition, and the food supply for birds and other predators. Readers curious about how insect diversity gets measured more broadly might enjoy comparing notes with a piece on how many types of butterflies exist worldwide, since butterflies and picture-winged flies both rely on patterned wings for very different survival strategies. The same decomposer role also links these flies to the wider conversation around endangered animals in North Dakota, many of which depend on healthy insect populations somewhere in their food chain.
Taken together, the ring-clawed deer fly, the bee-like robber fly, and the picture-winged fly show just how much variety hides inside a single insect order. One bites, one hunts, and one quietly recycles plant matter, yet all three are part of the same prairie ecosystem that supports everything from songbirds to the bats that patrol North Dakota’s night skies for flying insects. Anyone comparing notes across state lines can see how much overlap and difference exists by looking at the types of flies found in Delaware, a reminder that fly diversity shifts considerably even within a single country.