Do Banded Alder Borer Bite? Debunking Myths & Understanding Behavior

The banded alder borer (Rosalia funebris) is an exotic-looking beetle that may be encountered from March to August in the Pacific Northwest.

With their striking white-blue and black coloration, these insects can often be found on alder, ash, and California laurel trees, among other hardwoods1.

A common concern surrounding beetles like the banded alder borer is whether they bite humans. In this article, we will give you a comprehensive answer to this question

Do Banded Alder Borer Bite

Banded Alder Borer Beetle Identification and Description

Appearance and Colors

The Banded Alder Borer (Rosalia funebris) is a striking beetle with a unique color pattern. Its body displays:

  • Alternating black and white-blue bands
  • Distinct markings on the back

These colors and patterns often lead to confusion with the Asian Longhorn Beetle, an invasive pest.

Size and Body Structure

Banded Alder Borers are relatively large beetles, ranging in size from:

  • 1 inch to 1.6 inches in length
  • Cylindrical, elongated body shape

Their body structure allows them to easily bore through wood as they develop.

Antennae and Elytra

The Banded Alder Borer possesses:

  • Long, segmented black and white-blue antennae
  • Hard, protective elytra or wing covers

These features contribute to the overall striking appearance of this beetle.

Native Range and Ecosystem

The Banded Alder Borer (BAB) is native to the Pacific Northwest of the U.S and Canada1. It is often found in:

  • California
  • Oregon
  • Washington
  • British Columbia

Do Banded Alder Borer Bite?

Fortunately, they’re not typically known to bite people, especially not as a form of self-defense.

Instead, they use their mandibles (jaws) for feeding on the trees they inhabit. Which trees? We will discuss this is the next section.

However, it’s essential to remember that interactions with all insects should be approached with caution to avoid potential harm or allergic reactions.

Keep a respectful distance while observing these fascinating creatures in their natural habitat to ensure a safe and enjoyable experience.

Banded Alder Borer

Damage and Impact

Preferred Trees

The BAB prefers ecosystems near hardwood trees, including:

  • Alder
  • Ash
  • Willow
  • Oak
  • Maple
  • Poplar

Among these, the Banded Alder Borers have a preference for specific trees2. Primarily affecting:

  • Alder
  • Ash
  • California Laurel

Occasionally, they infest other hardwood trees. It’s important to monitor these affected trees for signs of BAB presence.

Living Trees

Banded alder borer (BATB) beetles primarily target living trees with weakened or injured bark.

These insects utilize their long antennae to detect trees in distress, causing further damage by boring into the bark and feeding on the inner layers. For example:

  • Weakened bark: BATB causes additional stress on trees already suffering from injuries or diseases
  • Frass: As they bore into the bark, beetles create sawdust-like waste, called frass

Banded Alder Borer

Dead or Dying Trees

BATB beetles also infest dead or dying trees, often speeding up the decomposition process of fallen or downed trees.

This can lead to increased firewood production as dead limbs and logs are broken down, creating new opportunities for pests.

Hardwoods

Roundheaded wood borers, like BATB, specifically target hardwoods.

They create extensive damage within the heartwood of these trees, further weakening the tree’s structure.

In the case of valuable timber, this can result in significant economic loss.

Agricultural and Landscape Impact

Though BATB do not typically cause widespread agricultural issues, they can still have a noticeable impact on the landscape. Key effects include:

  • Damaged trees: Dings and injuries caused by BATB in living trees can make them more susceptible to other pests or diseases
  • Dead wood: Infestations in dead or dying trees can lead to increased dead wood in the landscape

Overall, the damage and impact from BATB beetles can vary greatly depending on the targeted tree species, landscape, and other factors.

By better understanding these effects, homeowners, forest managers, and others can take necessary steps to mitigate BATB damage and protect our valuable trees and landscapes.

Banded Alder Borer

Signs of Banded Alder Borer Infestation

Fresh Paint and Flowers

Banded Alder Borer (BAB) adults are attracted to trees with fresh paint and flowers.

Their attraction is likely due to the similarities in scent between fresh paint and the pheromones emitted by other BABs.

When you see the adults on the tree trunks or branches, it can be an early sign of infestation.

Frass and Holes

Another sign of infestation are the frass and holes left behind by the borer larvae. Small holes in the tree bark indicate the presence of the larvae inside the tree.

  • Frass: Mixture of sawdust and fecal pellets, often reddish in color
  • Holes: Larval entrance and exit holes, can be detected on tree trunks or branches

As the larvae develop and feed on the tree, they create more holes, potentially weakening the tree and making it more susceptible to disease or other pests.

Banded Alder Borer

Control and Management

Cultural Care and Solutions

The Banded Alder Borer (BAB) is a native longhorned beetle belonging to the family Cerambycidae, known for its striking white-blue and black coloration.

BAB feeds on hardwood trees, primarily alder and ash, but occasionally other hardwoods such as California Laurel1.

Here are some cultural care solutions to manage and control this beetle:

Promote Tree Health: Healthy hardwood trees are less susceptible to borer infestations. Water and fertilize trees properly.

Monitor Infestations: Regularly inspect alder and other host trees for signs of borer activity (e.g., exit holes, tunneling).

Remove Infested Trees: Infested trees should be removed and properly discarded to prevent the spread of BAB to other trees.

Pros of Cultural Care SolutionsCons of Cultural Care Solutions
Promotes overall tree healthRequires ongoing maintenance
Can reduce borer infestationsMay not be 100% effective
Environmentally friendlyMay require professional help

Reporting Infestations

If you suspect a Banded Alder Borer infestation, it’s essential to report it to your County Agricultural Commissioner or appropriate authorities, as early detection can help manage and control the spread of this nuisance beetle.

Banded Alder Borer

Comparison with Other Beetles

Asian Longhorned Beetle

The Asian longhorned beetle is a highly destructive invasive species. It has long antennae and striking black and white coloring.

These beetles infest various hardwood trees, such as maple, elm, willow, and birch. Some features of the Asian longhorned beetle include:

  • Large size (up to 1.5 inches long)
  • Long antennae (longer than its body)
  • Black and white coloring

In comparison, the banded alder borer is less destructive and primarily infests dead or dying trees.

Both beetles are part of the longhorn beetles family, but their behavior and impact on the environment differ.

California Laurel Borer

The California laurel borer is another species of longhorn beetles. It is mainly found in California and infests bay laurel trees.

Some characteristics of the California laurel borer include:

  • Smaller size (approximately 0.5 inches long)
  • Long antennae
  • Black and gold coloring with iridescent blue-green wings

Though both the banded alder borer and the California laurel borer are part of the longhorn beetles family, they infest different tree species and have distinct color patterns.

Comparison Table:

FeatureBanded Alder BorerAsian Longhorned BeetleCalifornia Laurel Borer
Size1-1.5 inchesUp to 1.5 inchesApproximately 0.5 inches
Antennae LengthLongLonger than its bodyLong
ColoringBlack and whiteBlack and whiteBlack and gold
Trees InfestedAlder treesMaple, elm, willow, birchBay laurel trees
Impact on the EnvironmentLess DestructiveHighly DestructiveModerately Destructive

Conclusion

As we wrap up this comprehensive guide on the Banded Alder Borer, it’s crucial to debunk the myth that these beetles bite humans; they don’t. Instead, their mandibles are designed for feeding on trees.

These striking beetles, native to the Pacific Northwest, have a unique life cycle that involves laying eggs on specific host trees and larvae that tunnel into the wood, weakening the tree’s structure.

While they primarily target weakened or dying trees, their activity can exacerbate existing tree health issues. Monitoring for signs of infestation like frass and holes is vital for effective management.

Cultural care solutions, such as promoting tree health and removing infested trees, are recommended for controlling these native beetles.

Footnotes

  1. (https://entomology.oregonstate.edu/sites/agscid7/files/entomology/Banded_Alder%20Borer_13.pdf 2 3
  2. U.S. National Park Service – White Alder 

Reader Emails

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

Letter 1 – Battling Banded Alder Borers

what the heck are these?
Mr. Bugman.
My son and I were in pasadena,calif and we saw on a utility pole about 5 of these very scary looking bugs.. In one picture these bugs were fighting head to head and they even wrestled on the ground. What are these bugs and have you ever seen anything like these before?
thanks kayla and jason

Hi Kayla and Jason,
Even though your image is blurry, the distinctive markings of the Banded Alder Borer allow for instant identification. The two male Banded Alder Borers in your photo are battling over territory and a mate.

Letter 2 – Mating Banded Alder Borers

Hello bugman,
I live in Southern California and while I was on a lucnch break I spotted these bugs in Pasadena. I have never seen anything like these so I was wondering if maybe you could identify them for me. Thanks a bunch

These boldly beautiful beetles are Mating Banded Alder Borers, Rosalia funebris.

Letter 3 – Banded Alder Borer feeding on Daisy Pollen: Creative License

What is this
I photographed this flying insect the other day, can you tell me what it is? Location: Boise, Idaho Thanks,
Mitch York

Hi Mitch,
Under normal circumstances, we would not take the time to post an insect with two previous excellent postings within 24 hours, but your image is unique.

Your photo shows the Banded Alder Borer feeding on daily pollen, and in none of our research could we locate information on the adult food choices.

Though we suspected pollen and nectar, this is the first photo documentation we have received.

Confession: Photographer comes cleam
Daniel,
Thanks for the identification. I did not mean to mislead you with my photo, I actually put the Banded Alder Borer on the flower to be photographed.

I am a Professional Photographer and am always arranging my images for maximum effect. Best regards,
Mitch York

Letter 4 – Banded Alder Borer from Utah

Subject: Black and white insect
Location: Mentioned in letter
September 11, 2015 9:24 pm
Hiking in our Utah woods, several miles south of Salt Lake City, I found a dead insect: black and grayish white, wide, horizontal, uneven stripes on body and very evenly measured antennae. It has a black dot on it’s grayish white head.

The wings are about 1 inch long. I loved my entomology class in college years ago, now enjoy sketching and wish I’d pursued combining these for a profession instead of as an elem. school art teacher .

I couldn’t deal with the numbers of students, traveling to several schools with a team teacher, sigh. Thanks for helping to identify my specimen! Can still take and send photo if you need it.
Signature: Linda brigance

Banded Alder Borer
Banded Alder Borer

Dear Linda,
Banded Alder Borers with their impressive antennae are much more beautiful alive than your dead individual indicates. Based on BugGuide data, your sighting represents the easternmost range of a species normally found from California to the Pacific Northwest.

Letter 5 – First Banded Alder Borer of the season

Subject:  Insect
Geographic location of the bug:  Portland, or
Date: 07/15/2018
Time: 08:28 PM EDT
Your letter to the bugman:  What is this.
How you want your letter signed:  Bob

Banded Alder Borer

How very exciting Bob,
This is our first Banded Alder Borer of the season.

Authors

    by
  • 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.

  • 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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