Quick Answer
A clean, nearly round hole around 10-12 mm wide in unfinished or weathered wood can be consistent with a large carpenter-bee entrance. The hole alone is not proof: measure it, inspect the surrounding wood, and document bee activity or fresh excavation signs.
Evidence strength
Moderate with corroboration
A correctly sized round entrance in suitable wood becomes more meaningful with fresh shavings, staining, repeated use, or a verified carpenter bee.
- Diameter and a straight-on photograph help separate a round entrance from an irregular break.
- Protected undersides of eaves, rails, fascia, furniture, and trim are compatible locations.
- One old hole cannot establish current occupancy or hidden tunnel extent.
What it may indicate
- A carpenter bee nesting entrance leading into a tunnel excavated in wood.
- Past use when the hole is weathered and no fresh debris, staining, sound, or bee traffic is observed.
Other explanations
- A drilled fastener or construction hole; look for tool regularity, hardware history, and absence of excavation debris.
- Wood-boring beetle exits, which are often smaller and may occur with powder or numerous holes.
- Woodpecker, decay, or mechanical damage with irregular edges rather than a clean circular entrance.
- A pre-existing cavity used by another solitary bee or wasp rather than excavated by a carpenter bee.
What this evidence cannot prove
- Carpenter-bee identity from a hole without supporting evidence.
- Current occupancy, the number of bees, or whether brood is present.
- The internal tunnel length or structural condition of the wood.
- That every nearby bee is using that opening.
Where to check next
- Take a straight-on close-up beside a ruler and a wider image showing the whole wood member.
- Look for fresh coarse shavings, yellow-brown staining, audible activity, repeated round openings, or bee entry and exit.
- Check whether the wood is painted, weathered, decayed, or previously drilled before attributing the hole.
Additional evidence to collect
- A clear bee photograph that shows carpenter-bee features and its direct use of the opening.
- Repeated activity or new excavation material documented at the same measured hole.
- A qualified inspection when many openings or important structural wood is involved.
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Reviewed guidance
Last reviewed August 2026. This content supports evidence interpretation and does not replace medical diagnosis, structural inspection, product labels, or local rules.