Leptoglossus occidentalis (Western Conifer Seed Bug)

Leptoglossus occidentalis (Western Conifer Seed Bug)

It’s that time again, when outdoor bugs start looking for winter quarters indoors. We had 3 of these Western Conifer Seed Bugs in our apartment yesterday. They are harmless, although I did find an article talking about one in Europe that managed to stab someone with its proboscis, which is designed for sap sucking rather than poison injecting. And, though they are not stink bugs (Pentatomidae) they will release an unpleasant gas as a defense when threatened.

Leptoglossus occidentalis

These Hemiptera (true bugs) are members of the family Coreidae (leaf-footed bugs), so called because many members of the family have a leaf-like expansion of the hind tibia, as does Leptoglossus occidentalis. 

This species has antennae nearly as long as their body, and their body size ranges from 16-20mm. They are reddish brown with dark/light checkering of the wing margins, and often have a pale zigzag across the wings (hemelytra). The inner and outer expansion of the tibia is roughly equal in length. 

Western Conifer Seed Bug

They are native to western North America, and as the name implies, derive most of their nutrition from the seeds of conifers, although 1st instars will also suck the sap from needles and cone scales. They have expanded their range across the continent, and have recently been accidentally introduced into Europe, where they are considered a forest pest species.

Leptoglossus occidentalis

They are strong fliers, and produce a audible buzzing when in flight. But they are also very eye catching in flight, since it exposes their orange and black abdomen. Adults overwinter and lay eggs near new growth in the spring, which hatch in about 10 days. Nymphs reach adulthood in mid summer, but are most commonly seen in the fall when they are seeking winter shelter around homes. They are found region wide, wherever there are conifers. 

Western Conifer Seed Bug





Size- Length 16-24mm

Habitat- Coniferous trees

Range- Region wide

Eats- Sap from conifer seeds, cone scales, and needles 

Flight Season- Nymphs mature into adults in mid summer and over winter. Eggs are laid in spring.

Leptoglossus occidentalis (Western Conifer Seed Bug)

7 thoughts on “Leptoglossus occidentalis (Western Conifer Seed Bug)”

  1. These WC SBs are a problem to plumbing tubing (they can puncture it) . PEX has many articles about this particular bug, which I found after we installed radiant floor heat using PEX. I suppose that if they can puncture PEX , a washing machine hookup wouldn’t be too difficult…

    1. Wow, we built a house with PEX radiant floor heating (Kirkland, WA) and never heard about this. Glad we have since sold the house 🙂

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