Western Conifer Seed Bug, Stink Bug or Bed Bug? How to Identify the Bug in Your House
A big brown bug sitting still on the window frame. Another one crossing the living room with a loud buzz, like a bumblebee. A strange smell when you try to pick it up. Every fall, many Quebec homeowners find these insects inside and wonder the same thing: is this serious? In most cases, the answer is no. What you have found is most likely a western conifer seed bug or another stink bug looking for a place to spend the winter, not a bed bug. This guide helps you identify the bug in your house, understand why it got in, remove it without the smell and keep it from coming back.
The western conifer seed bug: the most common fall visitor
The western conifer seed bug (Leptoglossus occidentalis) is the large bug most often found in Quebec homes in the fall.
How to identify a western conifer seed bug
- Large size: about 2 cm (¾ inch) long, with a long, narrow body.
- Reddish-brown colour, with a thin whitish zigzag line across the middle of the back (sometimes faint).
- Hind legs widened into a small leaf shape: the easiest feature to spot, and the reason it belongs to the leaf-footed bug family.
- Long antennae and an abdomen patterned in yellow-orange and black, visible mostly when the wings are open.
- It buzzes when it flies: its noisy flight often startles people and gets it mistaken for a bee or bumblebee.
- It gives off a smell when handled or disturbed, an odd odour many people compare to pine resin.
Where does it come from?
Native to the Pacific coast, the western conifer seed bug began spreading east in the 1950s. According to Penn State Extension, it is now widespread across southern Canada and the northeastern United States. In summer, it feeds on the cones and seeds of conifers such as pines, spruces and hemlocks. It is not a threat to your trees or to your family.
The brown marmorated stink bug: worth watching, but still limited
The brown marmorated stink bug (Halyomorpha halys) is native to Asia. It gets a lot of attention because it causes serious crop damage where it is well established, and because it can invade homes in large numbers in parts of the United States.
How to identify a brown marmorated stink bug
According to the City of Montréal, the brown marmorated stink bug has:
- a shield-shaped body, yellowish-brown, marbled and speckled with black, 12 to 17 mm long;
- antennae with alternating pale and dark bands;
- alternating pale and dark bands along the edge of the abdomen;
- no small teeth on the cheeks or along the edges of the thorax.
These details matter because it closely resembles native stink bugs. If one of them is missing, you are most likely looking at a different species.
Is it in Quebec?
Its presence is still limited and closely monitored. A trapping network set up across southern Quebec from 2014 to 2017 caught relatively few brown marmorated stink bugs, almost all of them in urban areas, and signs of an established population in Montreal were reported from 2016 on (Phytoprotection, 2018). The City of Montréal now works with a national monitoring network to support early detection. In other words, the brown marmorated stink bug is in Quebec, but most big brown bugs found in homes are still western conifer seed bugs or native stink bugs.
Like the others, it moves into homes in the fall, cannot reproduce inside buildings and releases a foul-smelling substance when disturbed. The City of Montréal states that it poses no danger to human or animal health. If you think you have found one, take a clear photo so it can be properly identified.
Other stink bugs
In Quebec, people often call any shield-shaped bug a “wood bug” or a “brown bug”. These are stink bugs (family Pentatomidae), a group that includes several native species, brown or green. They earn their name by releasing a strong smell when they feel threatened. They normally live in gardens, fields and woods, and a few end up indoors in the fall, drawn by warm walls. They don’t bite people and don’t damage anything in the house.
What about boxelder bugs?
If your bug is smaller (about 12 mm), black with orange or red markings, and gathers by the dozen on a sunny wall, it is probably a boxelder bug. It behaves a bit like the western conifer seed bug, but in much larger numbers. We cover it in detail in our guide to boxelder bugs.
Western conifer seed bug or bed bug: how to tell the difference
This is the big worry, and it is easy to settle. Fall invaders and bed bugs have almost nothing in common:
- Size: an adult bed bug measures 5 to 7 mm, about the size of an apple seed. A western conifer seed bug is roughly three times longer.
- Wings: bed bugs have no wings and cannot fly. Western conifer seed bugs and stink bugs fly, sometimes noisily.
- Location: bed bugs hide in mattress seams, box springs and headboards, close to where you sleep. Fall invaders turn up near windows, exterior walls, light fixtures and sunny rooms.
- Diet: bed bugs feed on blood at night. Fall invaders feed on plants and don’t eat at all over the winter.
- Signs: a bed bug infestation leaves black spots, shed skins and small blood stains on bedding. Fall invaders leave nothing of the sort.
To compare with photos, see our guide What do bed bugs look like? And if you find signs in your bed, read what to do about bed bugs.
Comparison chart: which bug did you find?
| Insect | Size | Appearance | Key feature | Where you find it | Bites people? |
|---|---|---|---|---|---|
| Western conifer seed bug | about 20 mm | Reddish-brown, long and narrow | Leaf-shaped hind legs; buzzes in flight | Windows, walls, attics in the fall | No (extremely rare) |
| Brown marmorated stink bug | 12 to 17 mm | Marbled brown shield | Banded antennae and abdomen edge | Windows, walls in the fall | No |
| Native stink bug | about 1 to 1.5 cm | Brown or green shield | Lacks the full set of marmorated features | Gardens; sometimes homes in the fall | No |
| Boxelder bug | about 12 mm | Black and orange | Clusters by the dozen in the sun | South and west walls, then indoors in spring | No (extremely rare) |
| Bed bug | 5 to 7 mm | Brown, oval, flat, wingless | Cannot fly; signs on the mattress | Bed, box spring, couch | Yes, at night |
Why are there stink bugs in my house?
Western conifer seed bugs and brown marmorated stink bugs survive the winter as adults. Outdoors, they shelter under bark, in dead trees or under debris. Our homes offer something better: warm walls, dry attics and thousands of small gaps. From late August through October, they land on sunny walls and slip in through window seals, torn screens, soffits, vents and gaps around chimneys.
Once inside the walls or attic, they stay semi-dormant. On mild days, or when indoor heating warms a wall, some of them wander into living spaces, even in the middle of winter. They don’t reproduce indoors and don’t damage household items. In spring, the survivors try to make their way back outside.
How to get rid of stink bugs in the house without the smell
The golden rule: don’t squash them. You would release their odour, which can linger on your fingers or on fabric.
- Glass and cardboard: cover the bug with a glass, slide a piece of cardboard underneath and release it outside, away from the doors. It is the simplest method for one or two bugs.
- Soapy water: knock it into a jar of water with a few drops of dish soap. It won’t be able to climb out.
- Vacuum: handy when there are several. Empty it quickly into a sealed bag in the outdoor garbage, or the smell may linger.
- No insecticide indoors: sprays won’t stop more bugs from coming out of the walls and only add unnecessary products to your home. Colorado State University Extension recommends removing them one by one instead. See also our article on the dangers of over-the-counter insecticides.
How to keep stink bugs out of your house
Prevention happens between late August and late September, before the bugs start looking for shelter:
- re-caulk around windows, doors and trim;
- replace torn screens and worn weatherstripping;
- install door sweeps, including on the garage door;
- put fine mesh over attic and soffit vents and on the chimney cap;
- seal gaps around pipes and wires and cracks under the fascia;
- remove or cover window air conditioners before fall.
These steps also keep out other fall invaders, such as Asian lady beetles and cluster flies.
When should you call an exterminator?
A few western conifer seed bugs each fall don’t call for professional help. Call a pro if:
- you find bugs every day, in large numbers, despite sealing;
- the entry points are out of reach (second storey, soffits, roofline, attic);
- you manage a building or a business where the bugs bother tenants or customers;
- you are not sure they aren’t bed bugs. In that case, don’t wait: get the identification confirmed.
A technician can identify the insect, find the entry points and tell you whether an exterior perimeter treatment makes sense. Exterminatek offers outdoor spraying of exterior walls; see our pest control services. If it turns out to be bed bugs, our bed bug extermination service takes over.
Frequently asked questions
Do western conifer seed bugs bite?
No. The western conifer seed bug feeds on the sap of conifer cones and is not considered dangerous to people. The rare bites ever reported are exceptional and harmless. It can still be startling because of its size, its noisy flight and its smell.
Are brown marmorated stink bugs dangerous?
Not to your health. According to the City of Montréal, the brown marmorated stink bug poses no danger to human or animal health. It is mainly a nuisance in homes in the fall, and a crop pest where it is established.
Why do stink bugs smell when you crush them?
Western conifer seed bugs, brown marmorated stink bugs and other stink bugs have glands that release a smelly substance when they feel threatened. It is their defence against birds and other predators, which is why you should never squash them.
How can I tell if it’s a bed bug or a western conifer seed bug?
Look at the size and the wings. A bed bug is 5 to 7 mm long, has no wings and lives in your bed. A western conifer seed bug is about 2 cm long, flies and turns up near windows. If in doubt, photograph the insect next to a coin and compare it with our bed bug identification guide.
Need help identifying a bug?
Finding bugs in your house every day, or want to be sure they aren’t bed bugs? Our technicians can identify the insect, locate the entry points and recommend the right solution, anywhere in Greater Montreal. Call us at 514-677-7526 or request a quote.
