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Western conifer seed bug

The western conifer seed bug (*Leptoglossus occidentalis*) is a species of true bug in the family Coreidae.

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated July 27, 2026|2 min read| Fact-checked

The western conifer seed bug (Leptoglossus occidentalis) is a species of true bug in the family Coreidae. It is native to western North America and has spread widely across eastern North America and to parts of Europe and other regions. It feeds mainly on seeds and developing cones of conifers and is often noticed as a nuisance when adults enter buildings to overwinter.

Description

The western conifer seed bug is a large, brown leaf-footed bug with a distinctive white zigzag marking across the wings and flattened, leaf-like hind legs. Adults are typically about 9–18 mm long and are often confused with other insects because of their shape and colour.

Distribution

The species is native to western North America but has expanded eastward across the United States and Canada. It has also been introduced to parts of Europe and has established populations in some other regions.

Life history and feeding

This insect feeds primarily on seeds and developing cones of conifers, especially pines and Douglas-firs. Feeding usually causes little or no significant damage to healthy trees, though heavy seed-feeding can reduce some seeds.

Human interactions

Western conifer seed bugs commonly enter homes and other buildings in autumn to seek overwintering sites. They do not bite or sting, do not damage structures, and are mainly considered a nuisance pest.

Key facts

  • It is a true bug, also known as a leaf-footed bug.
  • Adults are reddish brown to brown and have leaf-like expansions on the hind legs.
  • It feeds mainly on pines, Douglas-firs, and other conifers.
  • It is generally harmless to people, pets, and buildings.
  • It often enters homes in late summer and fall to overwinter.
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Canadian context

The species is present in Canada, including provinces such as Ontario, Québec, New Brunswick, Nova Scotia, and Prince Edward Island, where it is mainly encountered as an overwintering nuisance in homes and buildings.

Frequently asked questions

What is the western conifer seed bug?
It is a species of true bug, Leptoglossus occidentalis, in the family Coreidae.
Where is it native to?
It is native to western North America west of the Rocky Mountains.
What does it eat?
It feeds mainly on seeds and developing cones of conifers such as pines and Douglas-firs.
Is it harmful to people or homes?
It is generally harmless to people, pets, and structures, though it can be a nuisance indoors.
Why do people find it in houses?
Adults enter buildings in late summer and fall to find protected places to overwinter.
Does it smell?
Yes. When disturbed or crushed, it can release a strong, pungent odour.

References

  1. Wikipediahttps://en.wikipedia.org/wiki/Western_conifer_seed_bug
    Supports: Scientific name, family, native range, introduced range, and general description.
  2. Royal Horticultural Societyhttps://www.rhs.org.uk/biodiversity/western-conifer-seed-bug
    Supports: Identification features, size, feeding on conifer cones, and presence in Europe.
  3. Montana State University Extensionhttps://urbanipm.montana.edu/entomology/resources/fact-sheets/nuisance_insect_pests/western.conifer.seedbug.html
    Supports: Size, feeding on pine and Douglas-fir seeds, overwintering in residences, and lack of significant tree damage.
  4. Michigan State University Extensionhttps://www.canr.msu.edu/resources/western-conifer-seed-bug
    Supports: Western origin, eastward spread, and nuisance entry into homes.
  5. Utah State University Extensionhttps://extension.usu.edu/planthealth/ipm/structural-pest-id-guide/western-conifer-seed-bug
    Supports: Identification, host plants, indoor overwintering, and lack of threat to human health.
  6. University of Minnesota Extensionhttps://entomology.umn.edu/western-conifer-seed-bug
    Supports: Description, feeding on cones and needles, and nuisance status indoors.