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Harmless

Western conifer seed bug

Leptoglossus occidentalis
Also called conifer seed bug, leaf-footed pine seed bug (loosely), WCSB

This big, slow bug looks alarming but does not bite people, spread disease or damage the house; it may give off a piney smell if handled.

Western conifer seed bug, photo 1
Photo: Gavin Slater, CC BY 4.0, via iNaturalist
Sizeabout 16–20 mm (5/8 to 3/4 inch) long
Where in the houseWindows and walls, attic, living room, bedroom, outside near the house
WhenSeptember and October as they move in, with a few showing up on warm days through winter and spring.

Check these features

  1. Long, narrow reddish-brown to dark brown bug
  2. Back legs have a flat, leaf-shaped flare partway down
  3. Thin zigzag white line across the middle of the back
  4. Yellow-orange and black patches on the abdomen, mostly seen when it flies
  5. Slow-moving; buzzes loudly when it flies

Bites and stings

Does not bite people. Only one bite has ever been recorded, and it caused brief itching and redness.

What to do

  1. Pick it up with a tissue, catch it in a cup, or vacuum it up; it is slow and easy to catch.
  2. Release or dispose of it outdoors, or empty the vacuum right away.
  3. Skip indoor sprays; they are not needed.
  4. Check for gaps around window frames, soffits and vents, where they usually get in.

Look-alikes

Kissing bug (conenose bug)Kissing bugs have a narrow, cone-shaped head, no leaf-like flare on the back legs, and red or orange marks around the flat outer edge of the abdomen; if you suspect one, do not crush it with bare hands and contact your extension office.
Brown marmorated stink bugThe stink bug is broad and shield-shaped with banded antennae, not long and narrow with flared back legs.
Squash bugSquash bugs are similar in color but have plain, thin back legs with no leaf-like flare.

Why it came inside

Adults spend the winter in sheltered places and crawl under siding and through small gaps into homes in fall, especially homes near pines and other conifers. They do not breed indoors.

Keep it out

  • Before September, replace loose or torn screens and caulk gaps around window and door frames.
  • Seal cracks behind chimneys and under fascia boards and soffits.
  • Screen attic, wall and chimney vents.
  • Add weatherstripping or door sweeps to doors that show light.

What helps

Links go to Amazon search results so you can compare current options. As an Amazon Associate I earn from qualifying purchases. Always follow the product label.

Vacuum with a hose

Lets you remove bugs, webs and egg sacs without touching them. Empty the bag or canister outside right away.

See options on Amazon
Bug catcher

A long-handled catcher moves a spider or insect outside without you having to touch it.

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Caulk and sealant

Silicone or siliconized acrylic caulk closes cracks around windows, pipes and baseboards. Bigger gaps need foam backer rod or expanding foam first.

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Screen repair kit

Patches or replaces torn window and door screens, one of the most common ways insects get in.

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Weatherstripping

Seals the gaps around doors and windows that let in drafts and bugs alike.

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Door sweep

Closes the gap under an exterior door. If you can see daylight under the door, bugs can get in.

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Sources

  1. Colorado State University Extension
  2. Montana State University Extension Urban IPM
  3. Penn State Extension
  4. Ohio State University Extension, Buckeye Yard & Garden onLine

Checked October 18, 2026. Rating backed by 3 sources. How we rate danger.