**Western Conifer Seed Bugs** (*Leptoglossus occidentalis*) are large **True Bugs** named for their primary host (conifers) and their origin in western North America. The conflict is **seed loss and structural nuisance**: in forests, they feed on developing conifer seeds, reducing timber yield. In residential areas, they are a major nuisance pest because they seek shelter indoors for the winter, often entering homes in large numbers, and release a strong, pungent, unpleasant odor when disturbed (**stink bug** behavior).
Taxonomy and Classification
Western Conifer Seed Bugs belong to the Order Hemiptera (True Bugs) and the Family Coreidae (Leaf-footed Bugs). They undergo simple metamorphosis.
Physical Description
Adults are large, 15 mm to 20 mm long.
- **Adult (Key ID):** Elongated, brownish body; characterized by the distinct **flattened, leaf-like flare** on their hind legs (hence “leaf-footed”); a prominent white or zigzag line across the middle of the back.
- **Damage ID:** Shriveled or empty conifer seeds; nuisance odor indoors; small fecal spots on walls/curtains (rare).
- **Conflict:** Structural (Nuisance), Forestry (Seed Damage).
Distribution and Habitat
Native to Western North America, but invasive and established across Europe. Habitat is conifer forests and surrounding urban areas; they overwinter inside heated structures.
Behavior and Conflict
The conflict is their overwintering behavior.
- **Overwintering:** They aggregate on the sunny side of buildings in the fall, seeking crevices and openings to enter wall voids for shelter.
- **Defense:** The odor released when crushed is due to volatile chemicals in their thoracic glands.
Management and Prevention
Management is **Exclusion and Mechanical Removal**.
- **Sealing:** Caulking and sealing all exterior cracks, window frames, utility entry points, and vents (with fine mesh) before the onset of cool weather in the fall.
- Using a vacuum cleaner to remove individuals found indoors (carefully, to avoid activating the odor).
Conservation and Research
Research focuses on their impact as an invasive species in European conifer forests and developing effective, non-chemical methods for exclusion from structures.