Plenty of the types of flies in Utah never bite anyone. A few of them protect gardens, pollinate flowers, or hunt wasps in midair.
Not every fly is that friendly. Along the Great Salt Lake, brine flies cover the shoreline. Two main described species live around the lake: Ephydra cineria is the most abundant, and Ephydra hians is the larger. Most visitors to Antelope Island find them harmless.
This guide covers 11 flies you can realistically meet in Utah yards, orchards, wetlands, and kitchens, with identification tips for each. It sticks to true flies (order Diptera). Anglers looking for fishing patterns should head to different types of flies for fishing. For a wider bug overview, see different types of insects.
Any list is only a sample. InsectIdentification.org counts over 20,000 known fly and mosquito species in North America alone. The table below gives a quick overview before the detailed profiles.
| Fly | What It Looks Like | Main Role |
|---|---|---|
| Robber Fly | Bristly, bearded, long-legged | Predator of other insects |
| Tephritid Fruit Fly | Small, with patterned wings | Plant feeder as larvae |
| Rabbit Bot Fly | Bulky and bee-like | Parasite of rabbits and rodents |
| Ornate Snipe Fly | Slender, long legs, marked wings | Soil-dwelling predator as larvae |
| Bee Fly | Fuzzy, round, long beak | Pollinator, parasite of bee larvae |
| Black Blow Fly | Shiny, metallic dark body | Decomposer |
| Common Oblique Syrphid Fly | Yellow and black abdomen bars | Pollinator, aphid predator |
| Filter Fly | Tiny, fuzzy, moth-like | Drain and sewage nuisance |
| Leaf Miner Fly | Tiny, dark with yellow | Leaf-tunneling plant pest |
| Transverse Flower Fly | Hairy, banded, bee-like | Pollinator |
| Small House Fly | Small and gray | Household nuisance |
1. Robber Fly
Robber flies are the ambush hunters of the fly world. The family Asilidae ranges from 3 to 50 mm long, and its members attack bees, wasps, dragonflies, grasshoppers, and other flies. Genera such as Efferia and Diogmites appear in North American robber fly listings.
The easiest identification cue is the face. Adults have a characteristic “beard” of hairs around the mouthparts. Look for a bristly body, long legs, and a habit of perching on a twig or rock and darting out at passing prey.
In Utah, robber flies tend to gather near forest edges and grasslands, so foothill trails and field margins are good places to watch. Local activity peaks in spring and summer, when prey is plentiful. Like spiders in Utah, they take live prey and help hold pest numbers down. The USU Extension beneficial insects guide calls them voracious predators that act as garden biological control.
Pro Tip: Robber flies inject a neurotoxin into their prey, so photograph them from a distance and never pinch one between your fingers.
2. Tephritid Fruit Fly
Tephritid fruit flies are often called picture-winged flies because of their patterned wings. Flies in the genus Trupanea are found throughout Utah. Their wings are held out and flicked in small displays, which makes them easy to tell from plain-winged flies.
These are not the tiny flies hovering over a fruit bowl. Kitchen fruit flies belong to a different family. Many tephritids develop inside flower heads of sunflower-family plants, and a few are orchard pests, such as the western cherry fruit fly (Rhagoletis indifferens).
If you spot a small fly with banded or netted wings walking jerkily across a daisy or sunflower bloom, it is probably a tephritid. They are harmless to people and usually need no control in home gardens.
3. Rabbit Bot Fly
Rabbit bot flies (Cuterebra species) are stocky, bee-sized flies that adults rarely use mouthparts on at all. You are more likely to meet the larvae than the adults. They grow under the skin of cottontails, jackrabbits, and rodents, forming a visible lump called a warble.
Each warble has a small breathing hole. In late summer and early fall, the full-grown larva leaves the host and drops to the soil to pupate. A warbled cottontail looks alarming, but healthy animals usually recover once the larva exits.
Key Insight: Never squeeze or pull a warble from a wild animal. A crushed larva can cause infection, and a veterinarian or wildlife rehabilitator should handle any pet or injured animal with one.
The adult fly is hard to find because it spends its short life near rodent burrows and rabbit runs. Seeing a warbled rabbit near your yard is the most common way Utah residents learn the species exists.
4. Ornate Snipe Fly
Snipe flies in the genus Chrysopilus are slender, long-legged flies with marked wings, and the ornate snipe fly gets its name from that decorated look. They belong to the family Rhagionidae. Adults rest on leaves and grasses and fly only short distances.
Use these cues to recognize one:
- A narrow, tapering abdomen and long, thin legs
- Wings with darker patches or a patterned tone
- A habit of sitting still on foliage in damp, shaded spots
- A rounded head with large eyes and no bee-like fuzz
The larvae live in moist soil and leaf litter and prey on other small invertebrates. Creek corridors and shaded canyon bottoms are better places to look than dry sagebrush flats. The ornate snipe fly does not bite people, though a few other snipe fly genera do. Readers curious about snipe flies in wetter woodlands can compare with types of flies in Massachusetts.
5. Bee Fly
Bee flies are fuzzy, round-bodied flies with a long, straight beak, and they hover at flowers like tiny helicopters. InsectIdentification.org’s Utah list includes bee flies in the genera Chrysanthrax, Hemipenthes, Poecilognathus, and Villa, plus Systoechus vulgaris. Its Utah insect directory is a useful photo reference.
Bee flies are harmless to people. The adults drink nectar. Their larvae, however, are parasites that feed on the grubs of ground-nesting bees and wasps. Females often flick eggs toward nest entrances while hovering overhead.
Three details separate a bee fly from a bee:
- Count the wings. A bee fly has one pair, while bees have two.
- Check the antennae, which are short on a fly.
- Look at the mouthparts. A long, rigid proboscis pointing forward means a bee fly.
Many species fly in spring and summer, with some appearing as soon as the first warm days. For another western comparison, read about types of flies in Oregon.
6. Black Blow Fly
The black blow fly (Phormia regina) has a shiny, metallic dark body, often with a greenish or bluish sheen. It is among the first insects to find a dead animal. Females lay eggs on carrion, and the larvae break the carcass down quickly. This is why blow flies matter to forensic investigators.
USU Extension lists blow and bottle flies among the common structural and health-related pests of Utah. They buzz heavily against windows and rarely bite. Outdoors they gather around garbage, pet waste, and kill sites.
Warning signs of a problem inside the home include:
- Several large, metallic flies appearing at once with no obvious source
- Flies clustering near a wall, vent, or crawl space
- A strong, sweet-rotten smell
A sudden swarm of large flies indoors often means an animal died in a wall void, attic, or crawl space. Removing the carcass solves the problem faster than any spray.
7. Common Oblique Syrphid Fly
The common oblique syrphid fly (Allograpta obliqua) is a small hover fly with slanting yellow bars across a dark abdomen. InsectIdentification.org’s Utah list includes the Common Oblique Syrphid Fly. It is one of the most useful flies a gardener can attract.
Syrphids are wasp and bee mimics, but they are harmless. According to the University of Minnesota Extension, syrphid flies do not bite or sting, and they show a single pair of wings where bees and wasps show two. The same source notes that one larva can eat dozens of aphids a day.
To bring them in, plant what the adults feed on. USU Extension’s guide lists carrot-family plants such as dill, fennel, and parsley, along with sunflower-family plants such as yarrow and cosmos. Skip broad-spectrum insecticides, because they kill aphid-eating larvae along with the pests.
8. Filter Fly
Filter flies, also called drain flies or moth flies, are tiny, fuzzy insects with wings held roof-like over the body. Many belong to the genus Psychoda. InsectIdentification.org’s Utah list includes the Filter Fly, and northern Utah pest control companies list drain flies among the common flies they treat. They live anywhere there are drains, from Salt Lake City to Texas.
Adults are weak fliers that hop along bathroom walls and sink edges. The larvae feed in the slimy film that coats drains, septic traps, and sewage filters. Larvae are rarely seen, but the adults point you to the source.
A simple home routine works for most infestations:
- Tape clear plastic over a suspect drain overnight. Flies trapped on the tape confirm the source.
- Scrub the pipe walls with a stiff brush to remove the film where larvae live.
- Flush the drain with hot water and repeat weekly for two to three weeks.
- Repair slow leaks and dry out damp areas under sinks.
9. Leaf Miner Fly
Leaf miner flies are small flies in the family Agromyzidae, and species of Liriomyza are common garden pests. The adults are only a couple of millimeters long, dark with yellow markings. You will rarely notice them. You will notice what the larvae do.
Larvae tunnel between the upper and lower leaf surfaces, leaving pale, winding trails in leaves. On a heavily mined leaf, the trails can merge into blotches. Vegetables and ornamentals are both targets, and the damage is mostly cosmetic on healthy plants.
Common Mistake: Spraying the leaf surface does little, because the larva is protected inside the leaf. Pick off and bag mined leaves instead.
Look for the trails in late spring and summer, then remove affected leaves early. Tiny parasitic wasps attack the larvae, so letting beneficial insects settle in helps long term.
10. Transverse Flower Fly
The transverse flower fly (Eristalis transversa) is a hairy, bee-like hover fly with orange and black markings on the abdomen. The Missouri Department of Conservation describes flower flies as harmless flies and valuable pollinators that mimic bees, wasps, and yellowjackets. North America has nearly 900 species. You can read more in its flower fly field guide.
The larvae of the Eristalis group live in stagnant, nutrient-rich water. They are the “rat-tailed maggots,” with a long tail-like breathing tube that reaches up to the water surface like a snorkel. That makes irrigation ditches, pond edges, and wet manure areas good breeding spots.
Adults visit asters, goldenrod, and other late bloomers well into fall, long after many native bees have gone quiet. A patch of late-season flowers is the best way to see one. For other creatures that share Utah gardens in summer, see fireflies in Utah.
11. Small House Fly
Small house flies are the indoor nuisance most people picture. The group includes the lesser house fly (Fannia canicularis), a slender gray fly smaller than the common house fly. Males hover in lazy circles in the middle of a room, often under a light, instead of landing on food.
The USU Extension pest guide lists the house fly among the common structural pests of Utah, and Rentokil’s northern Utah list does the same. Larvae develop in manure, rotting vegetation, and other wet organic waste. Adults reach homes through gaps and open doors, then breed if waste is left nearby.
Prevention follows the integrated pest management steps in the USU guide. Put them in this order:
- Clean dumpsters, trash cans, and the area around them regularly.
- Seal cracks around doors and windows.
- Fit screens to every window.
- Add weather stripping around doorways.
- Use fly light traps indoors for stragglers.
The 11 types of flies in Utah covered here range from predators and pollinators to household pests. A bearded face means a robber fly, a long beak means a bee fly, and a banded hover-flier on a flower means a syrphid. For comparisons beyond Utah, see the lists for insects in Ohio and insects in New York.