This article provides detailed information about the old house borer (Hylotrupes bajulus)—how to identify it, where it occurs in North America, how to prevent infestations, and how to eliminate it from homes and structures.
In North America, this pest is also referred to as the house longhorn beetle, woodboring beetle, or timber beetle, though “old house borer” is the most commonly used term.
What does the old house borer look like?
Adult old house borers are dark brown to black beetles, typically 8–25 mm (about ⅓ to 1 inch) long. They have a flattened, elongated body and two distinctive black, shiny spots on their thorax that resemble eyes. Their antennae are long—often about half the length of their bodies—giving them their alternative name: house longhorn beetle.
The larvae are creamy white, slightly curved, and can grow up to 30 mm (over 1 inch) in length. These larvae are responsible for the damage, as they bore through wood while feeding.
Where is the old house borer found in North America?
The old house borer is most commonly found in temperate regions of North America. It is widely established in parts of the Northeast, Midwest, and along both coastal regions, though it can occur in many other areas as well.
This woodboring pest is typically found:
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In homes with softwood framing, particularly pine
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In crawl spaces, attics, basements, and wall voids
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Behind wood paneling or siding
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In recently constructed homes (within the first 10–15 years) using infested timber
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Occasionally in antique furniture or reclaimed wood
It prefers drier wood with low moisture content, making seasoned softwood structures particularly vulnerable.
How can you recognize an old house borer infestation?
The signs of old house borer activity are often hidden until damage becomes significant. Early detection is challenging, especially since the larvae can remain inside wood for years before emerging.
Look for these key indicators:
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Oval exit holes (6–10 mm in diameter) on the surface of softwood
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Fine powdery frass (wood dust) near holes or along baseboards
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Hollow-sounding timber or weakened floorboards
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Clicking or rasping sounds coming from inside walls (made by feeding larvae)
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Dead adult beetles near windows or emerging from wood surfaces
While exit holes indicate past emergence, active infestations can only be confirmed by larval sounds or finding live insects.
Where does the old house borer live and breed?
Old house borers primarily infest softwoods like pine, fir, and spruce. Infestations usually begin when adult females lay eggs in cracks, joints, or exposed surfaces of wood. Once the eggs hatch, larvae tunnel into the timber and feed for several years.
They are commonly found in:
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Structural framing in homes
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Wooden beams and roof trusses
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Joists and subflooring
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Door and window frames made from softwood
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Occasionally in stored lumber, firewood, or reclaimed materials
Unlike many other wood-boring insects, old house borers can develop and spread inside dry, well-seasoned lumber used in construction.
What is the life cycle of the old house borer?
The old house borer has a long and variable life cycle, which depends on wood quality, temperature, and humidity.
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Eggs – Laid in cracks or joints in softwood surfaces.
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Larvae – Feed inside the wood for 2 to 10 years, depending on conditions.
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Pupae – Develop in a chamber near the wood surface for 2–4 weeks.
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Adults – Emerge during summer months, live a few days, and focus on reproduction.
This extended larval stage is what makes the pest particularly destructive and hard to detect early.
How can you prevent old house borer infestations?
Prevention is key to avoiding the costly damage associated with old house borers.
Inspect and treat lumber before use
Only use kiln-dried or pressure-treated lumber for construction. Avoid using reclaimed wood unless it has been professionally treated.
Control humidity levels
Keep indoor relative humidity low, especially in crawl spaces, attics, and basements. Proper ventilation and dehumidifiers can discourage infestation.
Seal exposed wood
Apply protective coatings like paint, varnish, or sealant to exposed wooden surfaces to reduce egg-laying opportunities.
Avoid storing untreated lumber indoors
Do not store raw or untreated wood inside the home or garage unless it has been inspected or treated for pests.
Monitor new construction
Homes built with softwood framing should be monitored periodically during the first 10–15 years, when infestations are most likely to appear.
How do you get rid of old house borers?
Eradicating the old house borer requires accurate identification and targeted treatment.
Confirm the infestation
A pest control professional can use acoustic detection, moisture meters, and other tools to confirm larval activity.
Remove and replace infested wood
In localized cases, the most effective method is to remove and replace the damaged wood entirely.
Use professional insecticidal treatment
Treatments may include injecting wood preservatives or borate-based products into active galleries. Surface sprays alone are typically ineffective.
Apply heat treatment
Heat treatment involves raising the temperature of infested structural wood to 120–140°F (49–60°C) for several hours to kill all life stages. This is often used in combination with chemical treatments.
Fumigation (for severe infestations)
In rare but serious cases, whole-structure fumigation may be required. This method is expensive and requires professional handling and temporary evacuation of the home.
Prevent reinfestation
After treatment, seal wood and reduce moisture to prevent future infestations. Continue monitoring vulnerable areas.
Are old house borers dangerous to people or pets?
Old house borers do not bite or sting and pose no direct harm to humans or animals. However, their structural damage can weaken homes over time, creating safety hazards and costly repairs. In heavily infested structures, floor sagging, cracked beams, and reduced structural integrity may occur.
By identifying and addressing infestations early, homeowners can minimize long-term damage and avoid expensive restoration work.
In which parts of North America are old house borers found?
Old house borers are widespread across temperate regions of North America. They are most commonly encountered in areas with high levels of residential construction using softwood framing. Homes built with imported lumber or located near wooded areas may be more susceptible.
Regions where they are commonly found include:
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Areas with humid summers and cold winters
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Regions with extensive pine or fir forests
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Residential zones with a high density of older softwood-framed homes
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Places with limited regulation of timber treatment
Their spread has increased with modern transportation of lumber, so infestations can now occur well beyond their original range. Regular inspections, careful lumber selection, and moisture control are the most reliable long-term defenses against the old house borer.