How Long Do Western Conifer Seed Bugs Live? Their Life Cycle Explained

Seed bugs are becoming common across North America. If you see some at home, you might wonder, “how long do western conifer seed bugs live?” Let’s find out.

The western conifer seed bugs, scientifically known as Leptoglossus occidentalis, are fascinating little creatures famous for their appearance and feeding habits. 

These insects have a short life cycle, producing just one generation a year. It emerges from its overwintering sites in late May and lasts till the onset of winter. 

Interestingly, most people assume that they are seed bugs, but technically, they are not (despite the name). They are actually leaf-footed bugs.

Here are a few things you should know about these bugs and how they live their brief lives. 


How Long Do Western Conifer Seed Bugs Live
Western Conifer Seed Bug


How Long Do They Live?

Western conifer seed bugs (also known as pine seed bugs) belong to the Coreidae family and rear only one generation a year. 

The life cycle of these bugs begins around June and August when adult Seed Bugs lay their eggs. Nymphs start growing every week, going through five instar stages. 

The average western conifer seed bug matures for over five weeks, living till the end of the summer. 

As one generation of the bugs dies in the summer, the new adults look for a place to overwinter and survive for the next season. 

This is the time when they are most likely to invade homes, looking for warmth and shelter.

How Many of Them Are There in the World?

Western Conifer bugs have a very rapid life cycle ranging in the late summers, so it is difficult to track their numbers in the world. 

Since they multiply quickly and within weeks of each generation dying out, we can safely say that their numbers are growing.

Moreover, this bug has been spreading rapidly across the US. It was first observed here in Michigan in 1987 but has since gone to many other states.


Western Conifer Seed Bug


Where Are They Found?

The western conifer seed bugs are native to the land west of the Rockies from California to British Columbia.

Over time, these bugs found their way to New Brunswick, Ontario, and Nova Scotia, mainly in areas abundant with pine cones. 

In the US, the bugs have moved to many states, including Maine, New York, Pennsylvania, Massachusetts, Connecticut, and New Hampshire. 

Outside North America, the bugs are found in parts of Mexico and Europe, where they were accidentally introduced.

These bugs move around places with pine cones and find warm areas to lay eggs. 

What Do They Feed On?

The name of these bugs mainly comes from their diet. They feed on coniferous fruits like douglas-fir seeds and certain types of pine cones.

The nymphs start by feeding on seeds that they find inside pinecones. 

The way they eat these seeds is also interesting. These bugs inject a special enzyme into the hard-shelled pine cones, which turns their insides into liquid.

After that, they suck the contents of the pinecones easily. 

What is Their Life Cycle Like?

The western conifer seed bug has a lifecycle that consists of four stages over five weeks. The egg stage lasts about two weeks, during which the eggs hatch and the nymphs emerge. 

Nymphs go through five instar stages before becoming adults, which takes about two months. 

The overwintering stage begins in late autumn when the bugs seek places to shelter from the cold weather. 

They remain in this stage until spring when they become active again and begin feeding on coniferous trees.


Western Conifer Seed Bug


Frequently Asked Questions

How do you keep western conifer seed bugs away?

If you are looking for a way to get rid of conifer bugs at home, you should start by finding gaps in your walls. 

Fill up gaps in window frames, and tighten loose ends of window screens and doors. Try to find small crevices and holes in the walls and fill them up with caulking.

Since they are big enough to be picked out, you can try removing them by hand, though it might not prove effective. 

Can western conifer seed bugs survive winter?

These bugs overwinter during the cold season, usually in places like buildings or the bark of trees.

The bugs try to find their way into homes where they find warmth in this season. 

You can notice them coming in through window cracks and wall vents with a loud, buzzing sound. 

What kills seed bugs?

For seed insects like conifer bug seeds, neem oil can be an effective solution. Spray neem oil on them and around areas where you see them hiding. 

There are also a few insecticides that can prove effective, but it’s best to avoid using them inside your home. 

Vacuum your walls and close small cracks and vents in walls and doorways to prevent them from entering. 

Do western conifer seed bugs harm trees?

Western conifer bugs get their name from their food source, coniferous trees.

They are not dangerous to a whole tree if it’s just one or two of them.

However, these bugs can multiply quickly, and a large infestation can easily kill a large tree. 

Wrap Up

They may not be potentially harmful bugs, but you need to look out for the Western Confier Seed bugs becoming a problem in your home. 

These reddish-brown, almost innocent-looking bugs may not live very long, but they multiply fast and can be very difficult to control. 

Thank you for reading, and watch out for the bugs! 

Reader Mails

Over the year, lots of our readers have found these bugs in and around the house. While most are benign, some have asked us how to get rid of them, and others are simply confused as to what they are.

Look at these emails and decide for yourself whether these bugs are a pest, nuisance, or just friendly neighborhood creepy crawlies!

Letter 1 – Squashed Western Conifer Seed Bug


What’s this bug
It’s the middle of winter here in Canada around -15C or so and I find this bug in the middle of my upstairs hall. Unfortunately my killer instincts kicked in, and I felt I had to protect my whole family from our strange house guest so I flattened it. Hopefully it’s resting peacefully in bug heaven and hopefully you can identify it.
Some things to note:
-We did have a live Christmas tree
-We have just recently completed renovations including new lumber
-After it was squished, there was a faint pine smell (could be my imagination b/c the guts were green)
Thanks for any help, and I look forward to getting your response.

Hi John,
I looks like you have dispatched a Western Conifer Seed Bug, Leptoglossus occidentalis, a member of the Big-Legged Bug Family Coreidae. Since they feed on pine seeds, it could have come in on your Christmas tree. They also seek shelter inside of homes to hibernate. They are harmless other than damaging pine seeds.

Letter 2 – Western Conifer Seed Bug Carnage (justified)


I hope you Can HELP
I am sorry to say I have killed three of these bugs in the last 2 months, one was much bigger than this one. I did not take pictures of that on. I live in upstate New York. Three pictures attached, I do hope you can assist me and tell me how to rid my house of these.
Thank you,

Dear GTW,
We don’t hold the swatting of Western Conifer Seed Bugs, Leptoglossus occidentalis, against you. This is an invasive species from Europe whose range is expanding.

Letter 3 – Western Conifer Seed Bug drowns in Aquarium in Poland


Subject:  Like a wasp in an aquarium
Geographic location of the bug:  Poland
Date: 11/28/2019
Time: 01:47 AM EDT
Your letter to the bugman:  I have found a bug in my aquarium with fishes. It was flat bug that looked even like it was made of plastic. Is it possible that it was growing in the aquarium?
How you want your letter signed:  Edie

Drowned Western Conifer Seed Bug

Dear Edie,
This is an invasive Western Conifer Seed Bug and it did not grow in your aquarium.  It must have fallen in and drowned.  This North American species, which is pictured on BugGuide, is invasive in Europe.

Letter 4 – Western Conifer Seed Bug


Subject: what kind of bug is this
Location: The Pinery Park Lake Huron shores Southwestern Ontario
October 13, 2013 6:59 am
Shot this picture near a public washroom in southwestern Ontario. Provincial park The Pinery. There were quite of few of them. Is this the dreaded Asian Long Horned Beetle?
Signature: David

Western Conifer Seed Bug
Western Conifer Seed Bug

Dear David,
This is a Western Conifer Seed Bug,
Leptoglossus occidentalis.  Though native to the Pacific Northwest, they have greatly expanded their range since the 1950s, probably with human intervention.  They frequently enter homes when the weather cools in order to hibernate through the winter.

Letter 5 – Western Conifer Seed Bug


Subject: cockroach?
Location: seattle, wa
October 31, 2013 1:23 am
Hi, I found this bug on my wall at midnight. I live in sesttle washington. Is it a roach?
Signature: bugman

Western Conifer Seed Bug
Western Conifer Seed Bug

This is not a Cockroach.  It is a Western Conifer Seed Bug, and it has greatly increased its range in the last fifty years.  Seattle is within the natural range of the species.  Western Conifer Seed Bugs often attract attention when the weather begins to cool as they are prone to entering homes to hibernate.


Letter 6 – Western Conifer Seed Bug


Subject: is this some kind of wasp?
Location: victoria bc
December 17, 2013 9:05 pm
Hi, I’ve seen this bug crawling on the window of the house, all I know that it fly’s, it walks slowly, and it smells rather old when you step on it (probably a defense mechanism). it look like an assassin bug but those live way the heck it the amazon. What is it? it look like halfway between spider and a wasp.
Signature: yes

Western Conifer Seed Bug
Western Conifer Seed Bug

This is a Western Conifer Seed Bug, and it is a Leaf Footed Bug or Big Legged Bug in the family Coreidae, not an Assassin Bug in the family Reduviidae.   The Western Conifer Seed Bug is a native species for you in British Columbia.  The range for the Western Conifer Seed Bug expanded significantly in the 1960s, and it is now found across much of the northern portion of North America.  The travel patterns of human most likely played a role in the range expansion, and in the early years of the 21st millennium, the Western Conifer Seed Bug was reported in northern Europe where it is now established.  This species has a habit of entering homes to hibernate when the weather cools, and that habit likely played a part in the range expansion with stowaways in suitcases.  The best way to avoid the smell produced when stepping on Western Conifer Seed Bugs is not to step on them.  We would also like to clarify your erroneous assumption that Assassin Bugs are only found in the Amazon.  There are different species in the Assassin Bug family found all over the world.

Letter 7 – Western Conifer Seed Bug


Subject: Borer Beetle??
Location: central New Hampshire
October 5, 2014 11:40 am
These beetles come into our house as the weather starts to get colder here in New England. Not sure how they get in. They are approx. 1-2 inches in length. I catch and release them back outside. My wife worries they are harmful to some of the native trees. What is this and is it a destructive critter?
Signature: bugged in NH

Western Conifer Seed Bug
Western Conifer Seed Bug

Dear bugged in NH,
Your description of this Western Conifer Seed Bug is accurate.  When the weather begins to cool, Western Conifer Seed Bugs often enter homes to hibernate, and though they can be a nuisance, they will not damage the home, its furnishings or its inhabitants.  The Western Conifer Seed Bug is native to the Pacific Northwest, but in the 1960s, due to a variety of factors that might include climate change and human travel patterns, the Western Conifer Seed Bug increased its range to include all of North America except the southeast.  The Western Conifer Seed Bug feeds upon “sap from green cones, twigs, seed pulp, and sometimes needles of Pinaceae (pines, hemlock, spruce, Douglas-fir)” according to BugGuide, but they do not harm the trees themselves.

Letter 8 – Western Conifer Seed Bug


Western Conifer Seed Bug
Western Conifer Seed Bug

Subject: Bug for identification
Location: Seattle, WA
October 10, 2014 7:09 pm
I live in Seattle, Washington and we have had a warm summer for us (80 degree days) and we are now entering our fall season and the temperature has dropped to the 70’s. I have had a few of these bugs at my house and many of my friends on Facebook have said they have them too and none of us know what they are and are hoping you can help us! We appreciate any information you can provide!!
Thank you!
Signature: Brenda

Dear Brenda,
The Western Conifer Seed Bug,
Leptoglossus occidentalis, is a native species to the Pacific Northwest, but beginning in the 1960s, perhaps due to increased mobility and travel, the range began to expand.  The Western Conifer Seed Bug is now well established in much of the northern part of North America, and in the early part of the 21st century, it became established in Europe as well.  Western Conifer Seed Bugs often go unnoticed until weather begins to cool and they enter homes to hibernate.

Letter 9 – Western Conifer Seed Bug


Subject: Marmorated Stink Bug but much prettier
Location: Somerville, Massachusetts
November 25, 2014 11:58 am
Hi, Can you help me ID this beautiful bug that’s been sitting on my garage door opener in Massachusetts. It is most similar in appearance to the
Marmorated Stink Bug, Halyomorpha halys Stål. However, the triangle
markings on its wings are very exotic and remind me of the Giant
Mesquite bug.
The underwings have 4 white bands
The back legs have 3 white bands
the antenna have 3 sections of increasingly lighter browns
The brown eyes extend outward from the head and are set on either side
of an elongated head
It has a white leaf/spade pattern painted on the the second section of
its body attached to the head.
The second part of triangle on its wings/back have outlined white
rectangles set at a 45-degree angle from the center line of the wing.
Signature: Miriam

Western Conifer Seed Bug
Western Conifer Seed Bug

Dear Miriam,
The Western Conifer Seed Bug,
Leptoglossus occidentalis, is native to the Pacific Northwest, but sometime in the 1960s, it began to expand its range.  We suspect the range expansion is connected to the increased frequency of human travel patterns.  Western Conifer Seed Bugs often attract attention when they enter homes to hibernate as the weather begins to cool.

Letter 10 – Western Conifer Seed Bug


Subject: Is it poisonous?!
Location: Ayr, Ontario (outside Cambridge)
October 20, 2015 7:26 pm
Hi there,
Thank you for existing! I’m terrified of this bug I just found 3 of in my home- when I killed it, a green liquid seeped into the paper towel that smelled like evergreen trees and was so strong. Can you tell me what it is and what I should do about it thank you so much.
Signature: Megan

Western Conifer Seed Bug
Western Conifer Seed Bug

Dear Megan,
The Western Conifer Seed Bug, a species that greatly expanded its range in the 1960s, probably by hitching rides with humans because of its hibernating habits.  Native to the Pacific Northwest, they are now found on the eastern portion of North America as well, and they have been introduced to Northern Europe very recently.  Western Conifer Seed Bugs frequently enter homes during the winter to hibernate.  Because they feed on the sap of pine cones, they retain the smell of the resins when mercilessly squashed.  They are not poisonous.

Letter 11 – Western Conifer Seed Bug


Subject: If beyonce was a bug
Location: Ontario, Canada
November 4, 2015 6:11 pm
I found this bug in my backyard, and I’ve never seen one like this before. I live in Ontario, and thought it looked pretty cool but I cant seem to find it on google anywhere. It’s about 1.5 inches long here’s a picture. Think you could help me out? ?
Signature:  Emily

Western Conifer Seed Bug
Western Conifer Seed Bug

Dear Emily,
Is the resemblance to Beyonce a reference to the shapely legs on this Western Conifer Seed Bug, one of the Big Legged Bugs in the family Coreidae?  The Western Conifer Seed Bug is native to the Pacific Northwest, but it greatly expanded its range in the 1960s, most likely because of its habit of hibernating in home when the weather cools, and then possibly stowing away in luggage at a time when air travel gained in popularity.

Western Conifer Seed Bug
Western Conifer Seed Bug

Letter 12 – Western Conifer Seed Bug


I live in Northern, NJ (Bergen County) and found this near my stove in the kitchen last night. Boy is it ugly!! Please let me know what it is as I spent over 1 hour looking online to try to see something similar but had no luck at all. I don’t think it is a roach (God I hope not!!!) – maybe some sort of Beetle? We have a very clean house and a dog if that matters. This site is great for us bugaphobes!!
New Jersey

Hi David,
You have a Western Conifer Seed Bug, Leptoglossus occidentalis, not a cockroach. We get lots of questions about them since they find their way into homes to hibernate. We have additional information on our True Bug page.


Letter 13 – Western Conifer Seed Bug enters a Mouse


Subject: Is this bug dangerous?
Location: Surrey, BC, Canada
November 20, 2015 11:17 pm
I live in British Columbia, Surrey, Canada and I see this bug all over Surrey in BC. Many times this bug tries to enter my mouse but I am scared this bug is dangerous or carries a disease like the jugu or whatever it is called disease. One time it did enter my house and it made this loud flopping of the wing and it looks huge and big and scary and I killed it…of course I was terrified to come close to it. This bug is super, super, super slow when it comes to walking.
Can you tell me what the name of the bug and if it is dangerous? Thanks
Signature: By email please.

Western Conifer Seed Bug
Western Conifer Seed Bug

This Western Conifer Seed Bug is not dangerous.  Western Conifer Seed Bugs often seek shelter indoors when weather turns colder, but we can’t understand why it is attempting to enter your mouse.

Sorry I meant house not mouse 🙂
People say that this bug as you described it: is called TRIATOMA INFESTANS BUG which will bring CHAGAS disease which literally is the 1st thought that came in my mind when I saw it. That is exactly that bug in my living room and washroom and I wish to confirm if it is true it is that dangerous chagas transmitting disease or not.

We don’t mean to disparage the internet as we are also an internet resource, but we don’t believe everything we read on the internet where any paranoid kook can write and post all manner of outrageously false information.  We have already identified your insect as a Western Conifer Seed Bug, Leptoglossus occidentalis.  Triatoma infestans, which does spread Chagas Disease, is a South American species, and the last time we checked a map, British Columbia is not located in South America with its namesake Colombia, though we could probably locate a map on the internet that places it there.  There are related members in the genus Triatoma found in North America, including the Eastern Blood Sucking Conenose Bug and the Western Blood Sucking Conenose Bug, but we reiterate, your insect is a harmless Western Conifer Seed Bug and it is NOT a member of the genus Triatoma.

Thank you 100% and I trust your professional information and I believe you 100% on what you said about the insect and also about the internet. I hope to ask you in the future with more insects I will see in the future and apologies if I offended you :). Just one question, if it lands on me or I handle it…would it bite me?

For the record, we are not entomologists, so we don’t have any professional credentials.  Like other internet sites, we often post incorrect information, but we strive for accuracy.  We do not take offense and no apologies are necessary.  We once heard it said that “if it has a mouth, it can bite” but we have not gotten any reports of people being bitten by Western Conifer Seed Bugs, though they do have mouths designed to pierce and suck fluids from seeds, so it is entirely possible that a bite could occur.  Please feel free to submit any future identification requests and we will try our best to respond.

Letter 14 – Western Conifer Seed Bug


Subject: Bug like QVC package..
Location: Willistown Twp, Chester County, PA
December 6, 2015 7:04 am
Hello bug man…
Is this a Western Conifer Seed bug??
Please advise.
Happy holidays!
Signature: Nancy

Western Conifer Seed Bug
Western Conifer Seed Bug

Hi Nancy,
This is a Western Conifer Seed Bug, and it seems it has settled into the packing material in an effort to find shelter from the oncoming winter weather.  This is exactly the type of behavior that we are speculating led to the range expansion of the Western Conifer Seed Bug beginning in the 1960s, when it spread from the Pacific Northwest to eventually include much of North America.  That was about the same time that air travel became more routine, and we believe the Western Conifer Seed Bug stowed away in luggage, eventually finding itself in a new time zone, and establishing itself in a new location.

Thx Daniel!
I ️hav  question …  A local news service make a stink about “deadly kissing bug”…that accord to my untraineyes look similar
To west. Conifer seed bug…
See their video Lin below— Are they mistaken?
PLESE let me know.
Thx SOMMUCh!!!
Kind regard,
Nancy. 🙂

Dear Nancy,
Your local news service is wrong.  The bug pictured in the video is a Western Conifer Seed Bug in the Leaf Footed Bug family Coreidae, NOT a Kissing Bug, a similar looking insect from the Assassin Bug Family Reduviidae.  There is currently much coverage on Kissing Bugs, that do spread Chagas Disease, but it is very irresponsible of your local news outlet to fuel paranoia by picturing the wrong insect in their coverage.  Sightings of Western Conifer Seed Bugs are much more common than sightings of Eastern Blood-Sucking Conenose Bugs or Kissing Bugs in your area.  You should write to your local news agency and inform them of their error and ask that they correct their posting.  They probably do not have an entomologist on the staff and the reporter did not do her due diligence by following up the submitted video with a local expert at a natural history museum.

That what I thought!!!! Thx for confirmation!  I WILL let THME know!  🙂

Letter 15 – Western Conifer Seed Bug


Subject: What in the world is this?
Location: Ohio
December 12, 2015 9:47 am
Found this bug on my screen door- live in a rural area of Ohio. Has been in the 40’s for a few days but has recently warmed to the 60’s today. Along with all the flies coming out, I saw this. It is overcast and slightly rainy today. We near open farm fields, have a small pond, creek and small woods.
Signature: Jen

Western Conifer Seed Bug
Western Conifer Seed Bug

Dear Jen,
As winter sets in, our identification requests for Western Conifer Seed Bugs increase as they seek shelter from the cold weather by coming indoors.  This year much media coverage on Kissing Bugs has caused many folks to write us to clarify the identity of Western Conifer Seed Bugs that superficially resemble Kissing Bugs.



  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

8 thoughts on “How Long Do Western Conifer Seed Bugs Live? Their Life Cycle Explained”

  1. I live in Digby, Nova Scotia, Canada and we have them in our house every fall. Never in the house except for this year. Hate these things 🙁 I never saw these as a kid, what’s up with them?

  2. Just this last Sunday I saw one of these critters on one of the windows after our potluck at church. I let it crawl around on my hand for a while and was going to let it fly to freedom, however it decided to hang out at one of the other windows near the doors. Not long after, some young (and probably naive) girl noticed it, grabbed a napkin, and uttering, “Eww, a bug,” snuffed out its life, in turn becoming revolted by the ensuing odor. I told her in a subtle tone it wouldn’t have hurt anyone (I didn’t want to sound like some PETA freak, lol) and that’s likely how they keep themselves from being eaten. But she said it was an ugly bug (???)

    Kristina A. Larson
    Ellsworth ME

  3. Thanks for the photo! I found one of these in my bathroom sink today. Thought sure it was a kissing bug, but after looking at a few photos, it seems to just be a seed bug. (Southwestern Ohio)


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