Bat Bugs in Utah Homes

The short version

If you find small, flat, reddish-brown bugs in a Utah home that has had bats in the attic or walls, they may not be bed bugs. Bat bugs are close relatives that feed on roosting bats. They look almost identical to bed bugs but need a different fix: deal with the bats first, then the bugs. Spraying the bedroom while a colony is still overhead treats the symptom and leaves the source in place.

Bat bugs in Utah

Utah State University Extension has warned that bed bugs have several look-alikes and closely related species that should be treated differently, "most notably western bat bugs (Cimex pilosellus)." USU's guide to common structural and health-related pests of Utah likewise notes that bed bugs look similar to bat and swallow bugs, and recommends identification by a professional entomologist. Colorado State University reports that the western bat bug is found throughout Colorado, while the eastern bat bug (Cimex adjunctus) occurs only in parts of eastern Colorado.

Bat bugs follow bats. About half of Utah's bat species use buildings, according to USU Extension, and the big brown bat is the most common bat in the state. In its July 2026 guidance, Utah DWR said female bats usually move into buildings in May or June to give birth. A colony that returns to the same attic year after year can support a population of bat bugs in the roost.

Bat bug or bed bug?

• Under magnification: the fringe hairs just behind a bat bug's head are longer than the width of its eye. A bed bug's are shorter. This is the feature the USU-hosted IPM manual and CSU both use.
• Where they turn up: CSU says bat bugs are found in the upper parts of buildings where bats roost, such as attics, wall voids, chimneys and under shingles. When they wander, they are most likely on the floor nearest the roost and are usually seen one at a time. Bed bugs gather in groups near beds, chairs and sofas.
• Host: bed bugs can reproduce on human blood. Bat bugs, swallow bugs and other bird bugs can bite people but cannot reproduce on human blood, CSU says.

Getting the identification right matters, because a bed bug treatment plan aimed at bedrooms won't touch bugs coming from an attic roost. The Utah Plant Pest Diagnostic Lab at USU in Logan identifies insects. It asks for photos first: text 385-367-3773 (texts only), or reach insect diagnostician Ernane Viera-Neto at 435-797-2435.

Why bites often start after the bats leave

As long as bats are in the roost, bat bugs mostly stay with them. The University of Missouri Extension explains that when bats are later excluded, the bugs leave the roosting area to look for a blood meal and can bite people nearby. According to CSU, bat bugs can live seven or eight months without feeding, may keep wandering through a structure for several months after the hosts are gone, and in some conditions survive more than a year.

That is not a reason to leave bats in place. It is a reason to plan the whole job:

1. Exclude the bats at the legal time. Bats are protected in Utah. DWR advises against sealing openings from May through August, when pups can't fly, and names fall as the best time. A permitted wildlife control company coordinates the removal with DWR.
2. Seal the paths into living space. CSU recommends sealing cracks around windows, gaps around electrical outlets and other openings in walls and ceilings, so wandering bugs can't reach bedrooms.
3. Clean up the roost. Removing guano and nesting debris takes away hiding places. See our guano cleanup guide.
4. Treat cracks and crevices if needed. CSU says residual insecticide dusts or sprays in cracks and crevices speed things up and recommends professional application. Missouri Extension notes that products labeled for bed bugs can be used in attics and wall voids. Always follow the label.

Don't handle bats while you're dealing with the bugs. Utah DHHS reports that every rabid animal found in Utah in 2025 was a bat. A bat found in a living space, especially where someone was sleeping, should be reported to your local health department.

Swallow bugs: the bird version

Birds have their own bed bug relatives. The swallow bug (Oeciacus vicarius) feeds mainly on cliff swallows, which build jug-shaped mud nests under eaves and overhangs. CSU says swallow bugs are most likely to bite people in spring, before the swallows return, or in autumn after they leave, when starving bugs go looking for another host. Cliff and barn swallows are on the federal list of protected migratory birds at 50 CFR 10.13, and under the Fish and Wildlife Service's 2025 nest memorandum, an active nest of a protected bird can't be destroyed without authorization. Remove empty nests after the young have fledged, and block the nesting spot before the birds return in spring. Other bird nests, such as starling and sparrow nests in vents, can carry bird mites; see our guide to birds in dryer vents.

What we do, and what we don't

Utah Wildlife Specialists handles the wildlife side: inspecting for bats, DWR-timed exclusion, sealing entry points, and guano and nest cleanup. We are not entomologists. If you're finding bugs, get them identified first, and for insecticide treatment use a licensed pest control applicator. A bat bug problem ends when the bats are permanently sealed out and the remaining bugs have nowhere to feed.

Related guides: signs of bats in the attic, are bats protected in Utah? and bats in winter. You can also browse our service area.

Common questions

Sources

1. Utah State University Extension: Utah Pests News, Winter 2010, "Bed Bugs in Utah" (PDF)
2. Utah State University Extension: Common Structural and Health-Related Pests of Utah (PDF)
3. IPM for Bed Bugs, chapter 8 of a University of Nebraska–Lincoln IPM manual, hosted by USU Extension (PDF)
4. Utah Plant Pest Diagnostic Lab (USU Extension): Contact us
5. Colorado State University, Agricultural Biology: Bed bug look-alikes (bat bugs and swallow bugs)
6. University of Missouri Extension G7396: Occasional Biting Pests
7. Utah State University Extension: Bats (Wildlife Damage Management Series, PDF)
8. Utah DWR: What to know about bats in Utah (July 14, 2026)
9. eCFR: 50 CFR 10.13, List of migratory birds
10. USFWS Migratory Bird Permit Memorandum MBPM-2-02: Authorizations to take migratory bird nests (Jan. 15, 2025, PDF)
11. Utah DHHS: Rabies Annual Report 2025