Life Cycle Of Western Conifer Seed Bug: How Long Does This Pest Live?

The western conifer seed bug is a very common pest in North America. In this article, we talk about the life cycle of western conifer seed bug, so that you know how long you will have to face this menace.

The Western Conifer Seed Bug (WCSB), is one of the main bugs of the Coreidae family. 

Found all around the US, these bugs were first found in Pennsylvania in July 1992 and are known for their habit of feeding on conifer seeds. 

But how do they grow up and live out their lives around conifer trees? In this article, let us tell you a bit about conifer seed bugs and their life cycle.

Life Cycle Of Western Conifer Bug
Western Conifer Seed Bug


The Western Conifer Seed Bugs reproduce as one generation every season. They lay eggs that hatch within ten days and feed on conifers. 

Despite the name, they are not seed bugs; they are from a family of leaf-footed bugs.

Their reproduction season lasts through August, and then they overwinter. 

The nymphs develop mouth-parts that let them feed on seeds and go through five stages before developing into adult bugs. 

Laying Eggs

The name of the bugs comes from their relation to their host conifers. 

Adult seed bugs overwinter in cold weather and emerge in the early summer months when they start feeding on pinecones and cone seeds. 

Females lay eggs in rows on the needles of coniferous trees, which include pine, red pine, spruce, and hemlock. 

The egg-laying season lasts from mid-June to early August, and these eggs take ten days to hatch. 


After hatching, the nymphs take around five weeks to mature as adults. The small ones feed on the soft tissue and needles of the cones. 

Over the next few weeks, the lives of these nymphs grow up and start feeding on ripe conifer seeds by early fall. 

For certain species, the reproduction process may differ. The species found in the US is known as Univoltine since they grow as a single generation every year. 

The Conifer seed bug species in Europe complete two generations every season, and some in tropical Mexico reproduce three generations every year. 

Life Cycle Of Western Conifer Bug
Western Conifer Seed Bug


At the end of every summer, one generation of Western conifer seed bugs dies out. The new generation of adults starts to overwinter and prepare for the next cycle. 

Most of the adults overwinter under the bark of pine trees and inside Douglas fir. 

These bugs also overwinter inside the nests of rodents and birds. In certain cases, for the lack of space, these bugs overwinter inside buildings. 


There are more than 30 species of trees that can become a Western Conifer bugs’ home. The common host conifers can be fir, spruce, pine, holly, cedar, and pistachio. 

These bugs are native to North America and are known to expand eastward, found as far as southern New Brunswick. 

These bugs were first found in Pennsylvania in the ‘90s and spotted moving North and Eastward. 

Their habitats were focused around the Pacific Northwest in the states of Washington, Oregon, and Idaho.

What Damage Do They Cause?

Western Conifer Seed Bugs are fairly harmless creatures that live off conifer trees in the wild. 

But if they are infesting conifer trees, there is a chance that the trees are in danger. And if you are living around a population of fir trees, your home could also be in trouble. 

Here are a few things you should know about conifer bugs being around you and your home. 

Damage To Douglas Fir Cones

One of the favorite trees for Western Conifer Seed Bugs to feast on is the Douglas fir. The nymphs and adults both feed off the needles, seeds, and cones of the Douglas fir, often resulting in the loss of the crop. 

The nymphs use their small mouthparts to feed on the sap and soft tissues of green cones and twigs. 

Life Cycle Of Western Conifer Bug
Western Conifer Seed Bug

While this may be harmless for the tree itself, the cones of fir trees can be damaged by extensive feeding of the bugs, resulting in the failure of the seeds to develop. 

In most cases, the bugs can have a direct impact on the growth and viability of conifer seed crops. 

Nuisance Pests During Winter

Western Conifer seed bugs are harmless in the sense that they do not bite or sting humans. But when they are making their way into homes and buildings, they can become a real nuisance. 

With areas that have a high population of conifer trees, the bugs can enter homes to overwinter. 

Sometimes with the high temperatures, the insects can become active indoors. In summer, they also move around from one tree to another, often entering homes. 

In a number of areas in the Northeastern US, these insects multiply at alarming rates in the overwintering months, finding a safe place from the cold temperatures. 

They are usually looking for warmth and shelter but cause an extremely disturbing odor when they attempt to be removed. 

Stink Bugs

WCSBs is a type of stink bug, ie, they give out a foul odor if they feel threatened, as a way to deter predators.

Many people who face these bugs often complain of the horrible stink they keep getting from their kitchens, bathrooms, attics, and other such places where these bugs hide.

Frequently Asked Questions

How do western conifer seed bugs get in your house?

Western conifer seed bugs enter homes through cracks in a building, wall voids, and, most commonly, through open windows. 
They usually try to find their way into homes in winter, looking for shelter and warm temperatures.

How do I get rid of western conifer seed bugs?

Eliminating gaps on window frames and tightening window screens can be the most effective way of keeping out conifer bugs. 
There is no insecticide that can be used on these leaf-footed bugs. Some of the small ones can be removed by hand.

Is the western conifer seed bug harmful?

The Western Conifer Seed Bugs are not harmful to humans directly since they do not bite or sting. They can become a nuisance in homes if they enter in large numbers and might require pest control to avoid an infestation.

Can western conifer seed bugs survive winter?

Wester Confider Seed bugs avoid winters because they cannot survive extremely cold temperatures. They try to find their way into buildings to overwinter, but they die out if they do not get enough moisture and the cover of conifer bark.

Wrap Up

So, unless there are seed bugs swarming your house all at once, you don’t have much to worry about the WCSB. They are wild creatures that stick to their habitat of coniferous trees, wandering into homes only when they are trying to be safe. 

Occasional pest control in extreme situations can help you live comfortably around them. Thank you for reading, and keep away from the pinecones in summer!


  • 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.

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  • 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.

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5 thoughts on “Life Cycle Of Western Conifer Seed Bug: How Long Does This Pest Live?”

  1. I am having the exact same problem right now across the Bay in Newark. I used to live in Los Altos and have never seen anything like this. It feels like a biblical plague. I’m glad I can now put a name to the pest … and that I’m not alone in having this weird infestation.

  2. I discovered a big herd of them all around our home located eastern Saudi Arabia. They are harmless creatures however, annoying as they hard to be tracked….they are just what you’ve captured


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