Identification
Adults are 18-20mm — very large for an indoor invader. Body is elongated and flattened, reddish-brown with a distinctive white zigzag pattern across the folded wings. The identifying feature is the hind leg tibias, which are dramatically flared and flattened into leaf-shaped expansions. Six legs total. Two long thin antennae. When disturbed they release a piney, fir-sap-like odour (related to their conifer diet, not unpleasant). Sometimes mistaken for assassin bugs, kissing bugs, or stink bugs by alarmed homeowners — it is none of these.
Habitat in BC
Outdoors in summer they feed on developing seeds of pine, fir, and Douglas-fir — a mild agricultural pest of seed orchards but not a significant one. In late September through October they seek overwintering sites and enter building envelopes through attic vents, soffit gaps, and window frames. Metro Vancouver homes near Douglas-fir forest edges, the North Shore, Anmore, and parts of Surrey and Langley with mature conifers see heaviest pressure. Not all of BC — more coastal and southern interior.
Signs you have western conifer seed bug
- Large reddish-brown leg-flared bugs flying slowly around house exteriors in September-October.
- Bugs crawling on walls, drapes, window sills inside the home in late winter and early spring.
- Distinctive piney odour when disturbed or crushed.
- Small dark fecal spots on window sills where they congregate.
Risk & damage
Zero. Western conifer seed bugs do not bite, do not transmit disease, do not damage structures, and do not infest food. The misidentification risk (homeowners think they're kissing bugs or assassin bugs) is the only real concern — Leptoglossus is completely harmless.
Seasonality in Metro Vancouver
Summer: feeding on conifer seeds outdoors in forested areas. Fall (September-November): overwintering migration to building envelopes. Winter: dormant in wall voids. Spring (February-April): emerging adults visible indoors. Not all conifer-adjacent BC homes see pressure every year; populations fluctuate with conifer seed crop success.
Treatment approach
Exclusion. Seal attic vents and soffit gaps with 6mm metal mesh in August-September before the migration. Vacuum indoor bugs with sealed disposal. No indoor pesticide treatment is appropriate — these bugs do no damage and killing them inside wall voids creates odour and secondary-pest issues.
When to call a professional
For small annual sightings, DIY vacuum + summer exclusion is fine. Call for professional service if you have large annual populations (often tied to a mature Douglas-fir directly beside the house), need documented exclusion for a renovation, or have a strata or apartment-building chronic-pressure situation.
Prevention playbook
How to prevent western conifer seed bug in Metro Vancouver homes
- 1
Seal attic vents and soffit gaps
In August, install 6mm galvanized metal mesh over attic vents, soffit gaps, and gable-end vents. These are the primary entry routes for Leptoglossus overwintering migration.
- 2
Audit window and door frames for gaps
Caulk gaps around window frames and install tight-fitting door sweeps on ground-floor exterior doors. Leptoglossus squeezes through surprisingly small gaps due to flattened body shape.
- 3
Consider conifer tree proximity
If a Douglas-fir, pine, or fir is directly adjacent to the house, it's the primary population source. Unless tree removal is already being considered for other reasons, the tree is valuable — accept the migration and focus on exclusion.
- 4
Vacuum indoor bugs, don't crush
Crushed Leptoglossus releases the defensive piney odour and can stain fabric. Use a vacuum with sealed disposable bag.
- 5
Don't use insecticides in wall voids
Dead bug accumulation in wall voids attracts secondary dermestid scavenger pests and creates odour issues. Exclusion prevents entry; vacuum handles what gets through.
The Wild Pest service
See our Western Conifer Seed Bug treatment page
Transparent pricing, 60-day return guarantee, same-day response across Metro Vancouver. Every treatment is documented with photos and service notes.
Frequently asked questions about western conifer seed bug
Is this a kissing bug or assassin bug?+
No. Western conifer seed bugs (Leptoglossus occidentalis) are often mistaken for kissing bugs (Triatoma) due to size and shape, but they are harmless herbivorous seed feeders. Kissing bugs do not occur in BC. If you find a large bug resembling the description, it's almost certainly Leptoglossus.
Do they bite?+
No. Their mouthparts are sucking stylets adapted for piercing seed cones and extracting plant material. They cannot bite or pierce human skin. They are completely harmless to people and pets.
What's that smell when I disturbed one?+
A defensive chemical released from thoracic scent glands. It smells piney or like Douglas-fir sap, which makes sense — they feed on Douglas-fir seeds and the compounds are related. Unpleasant but non-toxic.
Are they invasive?+
Native to the Pacific Northwest, so not invasive in BC. However, they've spread east across North America in the last several decades and are now considered invasive in eastern North America and in parts of Europe where they've been accidentally introduced.
Related species