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How to identify it
- Adults are red-brown or gray-brown, wingless and about 3/8 inch long, with oval bodies that are flat when unfed and swell after a blood meal.[1]
- They look so much like bed bugs that a hand lens or microscope is needed to tell them apart.[1][2]
- On a bat bug, the fringe hairs just behind the head are longer than the width of the eye; on a bed bug they are shorter.[1][4]
- Bat bugs are usually spotted one at a time on the upper floor near a roost, not in clusters around beds and sofas.[1]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Bed bug | Bed bugs feed and breed on people and hide near beds, chairs and sofas; their fringe hairs behind the head are shorter than the eye is wide.[1][4] |
| Swallow bug | Another close relative that feeds on cliff and barn swallows; its last two antenna segments are nearly equal in length.[1] |
Where it lives
Colorado State University reports the western bat bug across Colorado and the eastern bat bug in parts of eastern Colorado; both occur only in buildings that harbor roosting bats.[1]
Biology and life cycle
Bat bugs can only reproduce on the blood of bats, so they live around roosts in attics, between walls, in chimneys and under shingles.[1]
Eggs are laid in cracks near the roost, and nymphs feed to full in a few minutes, hide to digest, and molt several times before becoming adults.[1]
They often leave the bat after feeding but can ride in the folded wings of a resting bat to new roosts.[1]
Bat bugs can live seven or eight months without feeding, and under some conditions more than a year.[1]
Surveys have collected the eastern bat bug from bats and roosts in several states, including little brown bats in central Pennsylvania and colonies of Brazilian free-tailed and big brown bats in Georgia and Alabama.[5][6][7]
Damage and signs
- Bat bugs don't damage the building; the problem is bites when they wander into living areas after their bat hosts leave, die or are excluded.[1]
Health risk
Bat bugs can bite people but can't reproduce on human blood. The bats are the bigger health concern: CDC says bats are the most commonly reported rabid animals in the United States and that most people in the U.S. who die of rabies were exposed to a rabid bat. Don't touch bats, and talk to a healthcare provider or the health department after any contact.[1][8]
Control
Keep them out
The fix is to keep the bats from returning; without their hosts, bat bug infestations die out.[1][3][2]
Colorado State advises sealing entry points while bats are absent, October through early April, or using a one-way door in early spring before young are born.[1]
UC IPM advises against excluding colonies while flightless young may be present, usually May through September in California, and calls winter an ideal time.[2]
New Jersey allows bat exclusions only from April 1 to 30 and August 1 to October 15, bars them May 1 to July 31 while flightless young are in the roost, and restricts them October 16 to March 31 unless bats are shown to be absent, because some bats, especially big brown bats, overwinter in buildings. CDC says fall and winter are usually the best times and warns against trapping young bats inside from May to August.[9][8]
After the bats are out, seal cracks around windows, gaps around electrical outlets and other wall openings to keep wandering bat bugs out of living areas.[1]
Pesticides
Residual insecticide dusts or sprays in cracks and crevices can speed up elimination, focused on the roost; professional application is recommended. In a 2025 lab study, field-collected eastern bat bugs died from pyrethroid sprays and from deltamethrin and diatomaceous earth dusts about as readily as a susceptible bed bug strain, while two pyrethroid-resistant bed bug strains largely survived the sprays and deltamethrin dust.[1][3][10]
When to call a professional
Bats are legally protected and can carry rabies, so professional help with removal is highly recommended. New Jersey's guidelines say no lethal means or glue boards should be used on bats, and CDC notes that some bats are endangered and that local rules on removal apply.[1][9][8]
Where sources disagree
When to exclude bats: Colorado State advises sealing entry points while bats are absent, October through early April. UC IPM avoids May through September in California and calls winter ideal. New Jersey's state guidelines allow exclusions only in April and from August 1 to October 15, because bats may overwinter in buildings. CDC calls fall and winter the best times. Check your state wildlife agency before you seal anything.[1][2][9][8]
Which law protects bats: Colorado State says bats are protected under federal law. New Jersey's state law protects all native nongame wildlife, which covers its bats,, along with any federally listed endangered species, and CDC says some bats are endangered and local rules apply.[1][9][8]
Common questions
- Why did bugs start biting us after the bats left?
- When bats are excluded or die, hungry bat bugs move into living areas looking for another blood meal, and they can keep wandering for months.[1]
- Will bat bugs infest my bed like bed bugs?
- No. Bat bugs may bite people, but they can only reproduce on bats, so an infestation ends once the bats are gone and the remaining bugs die off.[1][2]
- How can I know whether it's a bat bug or a bed bug?
- Have an entomologist or pest professional examine a specimen; telling them apart takes magnification, and the answer changes where treatment is focused.[3][4][1]
- When is it safe to shut the bats out?
- When no flightless young are in the roost and the bats have left, usually fall or winter, though state rules differ: New Jersey, for example, permits exclusions only in April and from August 1 to October 15. Ask your state wildlife agency first.[8][2][9]
Sources
- Colorado State University, Department of Agricultural Biology, “Bed bug look-alikes (bat bugs, swallow bugs and relatives).” agsci.colostate.edu/agbio/ipm-pests/bed-bug-look-alikes/ (accessed 2026-11-11)
- University of California Statewide IPM Program, “Bats (Pest Notes, Home and Landscape).” ipm.ucanr.edu/home-and-landscape/bats/ (accessed 2026-11-11)
- University of Kentucky Entomology, “ENTFACT-636: Bed Bugs (revised March 2026).” entomology.mgcafe.uky.edu/ef636 (accessed 2026-11-11)
- University of California Statewide IPM Program, “Pest Notes: Bed Bugs, Publication 7454 (May 2013).” ipm.ucanr.edu/legacy_assets/PDF/PESTNOTES/pnbedbugs.pdf (accessed 2026-11-11)
- Journal of Medical Entomology, via PubMed, “Dick et al. (2003), Ectoparasite associations of bats from central Pennsylvania.” pubmed.ncbi.nlm.nih.gov/14765658/ (accessed 2026-11-11)
- Journal of Medical Entomology, via PubMed, “Spears, Durden and Hagan (1999), Ectoparasites of Brazilian free-tailed bats.” pubmed.ncbi.nlm.nih.gov/10467777/ (accessed 2026-11-11)
- Journal of Medical Entomology, via PubMed, “Durden et al. (1992), Ectoparasitic mites of sympatric Brazilian free-tailed bats and big brown bats in Alabama.” pubmed.ncbi.nlm.nih.gov/1625301/ (accessed 2026-11-11)
- Centers for Disease Control and Prevention, “Preventing Rabies from Bats (July 1, 2025).” www.cdc.gov/rabies/exposure/animals/bats.html (accessed 2026-11-11)
- New Jersey Division of Fish and Wildlife, Endangered and Nongame Species Program, “Nuisance Wildlife Control Guidelines for Bats (last updated Feb. 13, 2019).” nj.gov/dep/fgw/ensp/pdf/bat_control.pdf (accessed 2026-11-11)
- Journal of Economic Entomology, via PubMed, “Yu, Daramola and Wang (2025), Comparative susceptibility of the eastern bat bug and the common bed bug to selected insecticides.” pubmed.ncbi.nlm.nih.gov/41075310/ (accessed 2026-11-11)
- iNaturalist, “Cimex adjunctus taxon page (order and family).” www.inaturalist.org/taxa/453828 (accessed 2026-10-06)