Spined Oak Borer: Essential Facts for Tree Enthusiasts

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The Spined Oak Borer (Elaphidion mucronatum) is an intriguing insect that may have caught your attention in your backyard or the nearby woods. As a beetle in the family Cerambycidae, this unique creature can be spotted feasting on your oak trees. This article will serve as a beginner’s guide to the basics of the Spined Oak Borer, touching on its characteristics, life cycle, and other essential information.

Identifying these little creatures might initially be challenging, but with proper guidance, you will soon learn to spot them directly. Most commonly found in the eastern United States, the Spined Oak Borer has a tapered body form, boasting prominent spines on its thorax and wing covers. Their striking appearance can make them both fascinating and concerning to tree enthusiasts.

Familiarizing yourself with the Spined Oak Borer’s habits and preferred environments is essential for understanding its role in your local ecosystem. Although they may cause some damage to trees, their presence is typically not a cause for alarm. As you read further, you’ll find detailed insights about these unique insects and how they interact with their surroundings.

Understanding the Spined Oak Borer

Species Overview

The Spined Oak Borer (Elaphidion mucronatum) is an insect belonging to the longhorn beetles family. This beetle species is specifically known for infesting oak trees and occasionally other hardwoods. They can cause considerable damage to the trees, negatively affecting their health and growth.


  • Size: These beetles are relatively small, typically measuring around 1/2 to 3/4 inches in length.
  • Color: Their appearance is characterized by a dark brown or black color, with prominent, spine-like extensions protruding from their bodies.
  • Antennae: Like other longhorn beetles, they have long, segmented antennae, which are longer than their body.


Spined Oak Borers are primarily found in areas with an abundance of oak trees, as they depend on these trees for their survival and reproduction. They lay their eggs on the bark, and the larvae bore into the tree as they feed, creating tunnels and galleries in the process. This damages the tree and can lead to decay, or in severe cases, even tree death.

When dealing with Spined Oak Borer infestations, it’s essential to monitor and maintain your oak trees’ health, as these beetles tend to attack weak or stressed trees. Taking proper care of your trees, including regular pruning and ensuring sufficient water and nutrients, can help minimize the risk of beetle infestations and maintain a healthy ecosystem.

Life Cycle of the Spined Oak Borer

From Larvae to Beetle

The life cycle of the Spined Oak Borer starts as an egg. Once hatched, the larvae start to feed on the inner bark of oak trees. As they grow, they form tunnels in the tree, which can weaken it and potentially cause damage. After a period of growth and development, the larvae then transform into pupae. During this time, they prepare to transform into adult beetles.

Once mature, the adult beetles, also known as Moths, emerge from their pupae stage and begin the search for a mate. After mating, the female beetles lay their eggs on the bark of oak trees, and the cycle starts anew.

Seasonal Patterns

The Spined Oak Borer’s life cycle follows seasonal patterns. In general, larvae hatch and feed during warmer months, from spring to early summer. During this time, you may notice an increase in Spined Oak Borer activity around oak trees in your area.

As fall approaches, the larvae begin to pupate, and the adult Moths emerge. This is when they mate and lay their eggs on the host trees. During the winter months, the Spined Oak Borer’s activity slows down, and the cycle starts again in spring.

Remember, keeping an eye out for the seasonal patterns of the Spined Oak Borer is essential for managing their population and minimizing potential damage to oak trees in your area.

Host Plants and Impact

Common Host Trees

The Spined Oak Borer is an insect that primarily targets oak trees. However, it can also infest other hardwood trees and shrubs. Some common host trees include:

  • Red oaks
  • White oaks
  • Black oaks
  • Pin oaks

These trees are especially susceptible to infestation by the Spined Oak Borer.

Impact on Hardwoods

The Spined Oak Borer can cause significant damage to hardwood trees. It tunnels into the bark and wood, impacting the tree’s health and growth. When an infestation occurs, you may notice:

  • Dead branches
  • Yellowing leaves
  • Weakened tree structure

These symptoms can lead to an increase in the susceptibility of the tree to other diseases and pests.

Disease and Damage

Disease and damage caused by the Spined Oak Borer can have lasting effects on the health of your trees. As the borer feeds on the tree’s bark and wood, it creates:

  • Galleries or tunnels
  • Entry and exit holes in the bark

These damages result in disrupted nutrient and water flow within the tree, which can weaken the tree’s structure and eventually lead to its death. To protect your trees from the Spined Oak Borer, it’s essential to inspect them regularly and take necessary actions if an infestation is present.

Identifying the Spined Oak Borer

Physical Appearance

The Spined Oak Borer is an inch-long beetle with a distinct appearance. Its body is elongated and cylindrical, featuring a dark brown or black color. The beetle has spined, segmented antennae, which is a helpful feature when identifying it.

Behavior and Signs

This beetle is known for damaging oak trees and often leaves behind unique signs of infestation. You can look for these clues:

  • Patches of dead or dying bark on the oak tree
  • Small holes on the trunk, which is evidence of larval tunnels

Being familiar with the Spined Oak Borer’s appearance and the evidence of its presence will help you identify and address potential infestations effectively. Don’t forget to consult resources such as BugGuide or search for images online to further help you in identifying these invasive beetles.

Control and Management

Natural Predators

One effective way to control Spined Oak Borers is by relying on their natural predators, like woodpeckers and other insect-eating birds. These birds can help reduce the population of borers by feeding on them. To encourage the presence of woodpeckers around your oak trees, you can:

  • Create bird-friendly habitats around your property
  • Install birdhouses designed for woodpeckers
  • Avoid any actions or chemicals that might harm woodpeckers

Chemical Control Methods

In cases when the infestation is severe, you might need to consider using chemical control methods. Some options include:

  • Pesticides: Apply targeted pesticides to infested areas to control the borers. You should follow the manufacturer’s instructions closely and consult with a professional for optimal application.

  • Bait traps: Bait traps can be used to lure and trap the adult borers, helping reduce their population. These traps contain a pheromone attractant to draw the insects in.

Pros of chemical control methods:

  • Can provide immediate results
  • Effective in controlling severe infestations

Cons of chemical control methods:

  • Use of chemicals might harm non-target organisms like beneficial insects or birds
  • Overuse of chemicals can lead to resistant borer populations

It’s important to choose your control methods wisely and to monitor the situation to make sure the infestations are under control. In any case, always consult with a professional before applying any chemical treatments to your oak trees.

Spined Oak Borer Across North America

Distribution in the United States

The Spined Oak Borer (Elaphidion mucronatum) is native to North America and can be found in various regions across the United States. It primarily infests oak trees, specifically the Quercus species. The beetle’s distribution includes regions such as the Pacific Northwest, including states like Washington.

  • These beetles thrive in forests and woodland areas.
  • They are active during the warmer months, from April to September.

Presence in Canada

In Canada, the Spined Oak Borer can also be found within the country’s oak tree populations. Oak trees are native to various provinces, creating suitable habitats for the Spined Oak Borer.

  • Oak trees are common in southern Canada, especially in regions like Ontario, Quebec, and Manitoba.
  • Keep an eye out for signs of infestation, such as small holes in the bark or the presence of the borer’s larvae.

In short, it’s essential to monitor and manage the Spined Oak Borer’s presence to protect the health and longevity of oak trees both in the United States and Canada. Remember to stay vigilant and proactively deal with potential infestations in your area.

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Spined Oak Borer


Beautiful brown beetle
July 13, 2009
This was taken on Sat. (July the 10h) in Charlotte, NC. We had a huge yardsale (we made $666.25) and the door to the house was open and this fella was on the kitchen wall. I am on WTB daily and often use it to identify things that I cannot readily identify. I love this site! The beetle (a longicorn possibly) was about an inch long. I took some photos and then let him out into the woods behind the house.
Brian R. Lucas
Charlotte, NC

Spined Oak Borer
Spined Oak Borer

Thanks for your nice letter Brian,
This is a Spined Oak Borer, Elaphidion mucranatum.  According to BugGuide:  “Eggs are laid beneath bark of dead hardwoods. Larvae feed beneath the bark for the first year and feed deeper the second year. Adults come to lights, bait traps.

Excellent I can add that one to my collection of insects I can identify.  I had a huge Chalcophora virginiensis land on me at the Reedy Creek Nature preserve here in charlotte a few months back and it totally freaked out the guys I was playing disc golf with (I play almost every day) I got to identify it and tell them about itt. I am now the “bug guy” for our club I identify and inform people about all the neat bugs (and additionally reptile/amphibians) on our courses. Unfortunately I wasn’t able to get a picture of the lime green assassin bug that visited the yard sale.  You guys rock, and condolences on the fishes.

Thanks for the condolences Brian.  There will be more fish soon enough.  The sad part is that we rescued them from the community aquarium and kept them alone and fed them for four days.  We just misjudged what a young Angelfish will try to put in its mouth.  We won’t make that mistake again.

Letter 2 – Spined Oak Borer


“Granddaddy” bug speaks
June 29, 2010
Just wanted to say first of all that I love your website, I always come here when I’m trying to identify a bug or spider that as wondered into my home. This bug here which to me looks “old” in the face and thats why I call him the “granddaddy” bug, flew or fell onto my arm 4 nights ago as I set at my computer desk. Im not for sure that he flys so much because he just was there on my arm. I kept him intil the next day so I could get some good pics outside before I let him go. In the one pic where I held him up so you could get a good look at his face, he did try and bite me, which was ok, if someone 100 times bigger than me was holding me like that I would try and bite them too, lol. His shell is really hard and he makes the neatest “singing&qu ot; noise as if he is trying to speak. After I snapped the pics I of course let him go unharmed .
“curious about bugs”
Dryden VA (Lee Co)

Spined Oak Borer

Dear curious about bugs,
Thanks for the compliments.  Your Longhorn Beetle in the family Cerambycidae is a Spined Oak Borer, Elaphidion mucronatum.  You can compare your specimen to this photo on BugGuide.  Earlier in June, we posted a letter with a misidentified Spined Oak Borer, and you can read about how Karl provided us with a correction.

Spined Oak Borer

Letter 3 – Spined Oak Borer


Subject:n  What is this?
Geographic location of the bug:  Eastern Pennsylvania 19504
Date: 03/30/2019
Time: 09:56 AM EDT
Your letter to the bugman:  Second one of these we found in our home this week.  One in our living room, one in our kitchen. Wondering what it is and if we may have more. Found mid to late March 2019. Legs damaged in capture.
How you want your letter signed:  Curious homeowner

Spined Oak Borer

Dear Curious homeowner,
Do you have a fireplace or wood burning stove and do you store firewood inside the home?  This is a Spined Oak Borer,
Elaphidion mucronatum, which we identified on BugGuide, and according to BugGuide:  “Extremely polyphagous; hosts include most eastern hardwoods & shrubs.  Also noted in bald cypress (Taxodium distichum)” and “Eggs are laid beneath bark of dead hardwoods. Larvae feed beneath the bark for the first year and feed deeper the second year.”  Adults do not feed on wood.  We are presuming the individuals you found in your home emerged from wood you brought indoors.

Letter 4 – Spined Bark Borer


it’s a longhorned beetle, but what kind? Dear Bug Person, I found this on a coffee singles package this morning in our warehouse. I live in Spartanburg, SC and cannot tell if this is a Carolina Sawyer beetle or not. It has larger pincers than the sawyer beetle. We do receive foriegn shipments, maybe he hopped a ride overseas?!
Shane G

Hi Shane,
When we aren’t sure, we turn to entomologist Eric Eaton who usually knows the correct answer. Here is what he has to say: “My best guess is the “spined bark borer,” Elaphidion mucronatum. Those spines on the antennae are distinctive. Certainly that genus anyway.


  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com 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.

    View all posts
  • 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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Tags: Spined Oak Borers

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2 Comments. Leave new

  • Hello. I was just wondering if these insects were harmful to humans. Do they bite and can they infest a house?

  • I live in kirtland, N.M.
    I found one of these on the top of my ceiling. I also want to know if it is dangerous


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