Brown Prionid Beetle Bite: Is It Poisonous? Find Out Now!

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The brown prionid beetle is a type of long-horned beetle known for its distinctive appearance and wood-boring habits.

While beetles from other families, such as cerambycids, have been known to be troublesome pests inside homes, it’s natural to be curious about whether or not the brown prionid beetle presents any danger to humans.

Brown Prionid Beetle Bite

When it comes to beetles of this nature, a common concern is if their bite is poisonous.

Examining this is important, as many other insects, such as wasps and spiders, can cause significant harm through venomous bites or stings.

It’s essential to understand the potential risks associated with brown prionid beetles and similar species.

Brown Prionid Beetle Overview

Classification and Description

The Brown Prionid (Orthosoma brunneum) is an insect belonging to the family Cerambycidae, also known as longhorn beetles.

This species falls under the genus Orthosoma within the subfamily Prioninae and tribe Prionini. As part of the order Coleoptera, these beetles are classified in the class Insecta, within the phylum Arthropoda and kingdom Animalia.

  • Size: Adult Brown Prionids can grow up to 1.5 inches long
  • Color: They have a distinct reddish-brown to dark brown coloration

Habitat and Distribution

Brown Prionids are native species commonly found across the United States. They reside in various habitats, such as:

  • Forest edges
  • Woodlands
  • Rotting logs or stumps

Life Cycle and Diet

The life cycle of Brown Prionids includes the following stages:

  1. Egg
  2. Larva
  3. Pupa
  4. Adult

Larvae of these beetles are cream to brown in color and grow up to 3 inches in length over a three to five-year period.

They primarily feed on decaying wood, while adult beetles consume tree sap and plant nectar.

Brown Prionid Beetle Bite Characteristics

Physical Features

The brown prionid beetle has strong mandibles that can deliver a bite. However, their bite is not poisonous. Key physical features of the bite are:

  • A small puncture mark
  • Minor bleeding

Pain and Swelling

Bites from brown prionid beetles can cause some pain and swelling. Symptoms may include:

  • Mild to moderate pain
  • Localized redness
  • Swelling around the bite area

Comparison with Other Insect Bites

Comparing brown prionid beetle bites to other insect bites:

Insect Bite Symptoms Poisonous?
Brown prionid Pain, redness, swelling No
Spider Variable, may cause severe pain, necrosis Some species
Mosquito Itchiness, redness, swelling No
Cockroach Red, itchiness No

The brown prionid beetle bite is generally less severe than some spider bites and involves fewer symptoms than those caused by mosquitoes and cockroaches.

Remember to seek medical advice if symptoms worsen or persist, as individual reactions may vary.

Is the Brown Prionid Beetle Poisonous?

The Brown Prionid Beetle, also known as the California Prionus, is a type of beetle that can cause concern due to its large size and powerful mandibles.

However, it is important to know if a bite from this beetle is poisonous or not.

  • Venom: Brown Prionid Beetles do not produce venom. They primarily feed on plant materials and do not have a venomous bite.

A bite from a Brown Prionid Beetle can cause some symptoms, but they are generally mild and not life-threatening.

  • Local reaction: A bite may result in a red mark on the skin. This is a typical response to physical trauma from the beetle’s strong mandibles.
  • Discomfort: Some discomfort may follow a bite due to the pressure exerted by the beetle’s jaws.

Despite the lack of venom and mild reactions to a bite, it is essential to take some precautions around Brown Prionid Beetles:

  • Do not handle them with bare hands; instead, use gloves or tools if necessary.
  • Keep a safe distance when observing these beetles in the wild.

In summary, Brown Prionid Beetles are not poisonous, and their bites are not venomous. However, it is crucial to be cautious around them and handle them with care if needed.

First Aid and Prevention

Immediate Treatment

If bitten by a brown prionid beetle, it’s vital to clean the wound with soapy water immediately. This helps reduce the risk of infections.

Possible Infections and Complications

Although brown prionid beetle bites aren’t poisonous, there can be risks of infections or complications.

Some people might experience an allergic reaction to the bite. Also, an unclean bite can lead to infections, which may cause diseases.

Protective Measures

To prevent brown prionid beetle bites, follow these measures:

  • Wear long pants and long-sleeved shirts, which can reduce direct contact with beetles.
  • Avoid handling or disturbing the beetles.

Brown Prionid Beetle Infestation

Signs of Infestation

Brown Prionid Beetles can cause damage to various plants and trees, with a particular preference for decaying wood. Some signs that these beetles have infested an area include:

  • Presence of adults: Adult beetles are relatively large, with a length ranging from 1-1.5 inches. They have a cylindrical body and can be easily identified by their dark chestnut-brown color.
  • Larvae in moist decaying wood: Brown prionid larvae favor moist decaying wood as their primary habitat. If you come across larvae in such areas, it is a sign of infestation.
  • Exiting holes on wood: When the larvae finish their development, they will create exit holes in the wood.

Potential Damage

Brown Prionid Beetles are known as root borers, and their larval stage can cause significant damage to the roots of various plants and trees including oak and firs.

The primary damages caused by these beetles are:

  • Weakening of structural integrity: The infestation can weaken the overall structural integrity of the affected trees, eventually leading to their collapse.
  • Death of plants and trees: Prolonged infestations can ultimately lead to the death of plants and trees as their roots are damaged over time.

Control Measures

Effective control measures to manage a Brown Prionid Beetle infestation are:

  • Removal of decaying wood: As the larvae prefer moist decaying wood, removing these materials from your property can significantly reduce the chances of an infestation.
  • Trimming of shrubs: Maintaining proper landscaping by pruning shrubs and eliminating excess vegetation impedes the beetle’s access to potential host plants.
  • Chemical treatments: In cases of severe infestation, applying appropriate insecticides targeting both adult beetles and larvae may be necessary.

It is essential to monitor and identify potential infestations early to prevent significant damage to plants and trees.

Additionally, as the Brown Prionid Beetle is primarily an outdoor pest, infestations rarely occur inside structures such as basements or attics.

However, these beetles are not poisonous to humans or pets, so the primary concern should be focused on the potential damage they can cause to plants and trees.


The Brown Prionid Beetle, with its distinctive appearance and wood-boring habits, often piques human curiosity.

While their size and strong mandibles might seem intimidating, it’s reassuring to know that these beetles are not poisonous and their bites, though potentially painful, are not venomous.

Their primary diet consists of decaying wood and plant nectar, and they play a significant role in the ecosystem by aiding in the decomposition process.

However, like many insects, they can become problematic in large numbers, especially when their feeding habits lead to damage to plants and trees.

It’s essential to recognize their presence, understand their behavior, and take appropriate measures if needed, always keeping in mind the balance of nature.



Reader Emails

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

Letter 1 – Prionid from Florida: Stenodontes chevrolati we believe

Subject: Devils coach horse – in Florida?
Location: Spring Hill, Florida
August 12, 2017 7:10 pm
Found this beetle in some logs in Central Florida, being from the U.K. I thought it resembled a Devil’s Coach Horse beetle but I don’t think they are in Florida. What do you reckon?
Signature: Rob

Prionid: Stenodontes chevrolati perhaps

Dear Rob,
This is definitely not a Devil’s Coachhorse, a species of Rove Beetle.  This is a Stump Borer in the subfamily Prioninae.  We believe we have correctly identified it as
Stenodontes chevrolati thanks to this BugGuide image.


Letter 2 – Mounted Prionid Beetle from Chile

Big Big Beetle from Chile?
Fri, Dec 5, 2008 at 11:56 AM
My grandfather caught and mounted this bug for me when I was a baby. But his intricate calligraphy has faded off the little identification sticker. Can someone enlighten me, what is the name of this insect? It is framed with the title “Coleopteros Chilenos” and is about 5 inches in size.
Carol A.

Beetle Collection from Chile
Beetle Collection from Chile:  Conognatha fisheri, Acanthinodera cummingi and Tauroceraste patagonicus.

Hi Carol,
We can tell you that this is a Prionid Beetle in the subfamily Prioninae, but we are going to have to rely on the assistance of an expert in taxonomy to provide you with a species name.  You are very lucky to have inherited such a nice collection from your grandfather.

Update:  May 24, 2014
Thanks to a comment from Dolan Pinto, we have added the species names to the three beetles visible in the image above, including the Prionid,
Acanthinodera cummingi.

Letter 3 – Prionid

Subject: Biiiig Beetle in the High Desert
Location: Sandia Park, NM
July 5, 2017 11:33 am
We found this huge beetle-like bug in Sandia Park, NM (just over 7,000 ft) on 7/3/17. I have never seen an insect this large in NM. Any idea what it might be? This was how we found and left it… it was 11pm as we were leaving a local house…
Signature: Kzrivera


Dear Kzrivera,
This is one of the Root Borers in the genus
Prionus, and there are several similar looking species found in New Mexico.  We cannot determine the exact species at this time.

Thank you Daniel.
That is how I found you, searching for a match and seeing a similar image with a different root borer (different body shape) on your website.
This is a great service you provide! We are moving from Albuquerque to Sandia Park and want to understand our new “neighbors.”

Letter 4 – Prionid from Australia: Agrianome spinicollis

Subject: Big beetle id please
Location: Lake Macquarie NSW
December 12, 2016 8:52 pm
Hi, I’ve seen this beetle today for the first time, although my partner says he has seen it on the tree before. I have never seen one like it. It’s very big, about 60mm and appears to have been living on a sawn off palm trunk.

I’m at Wyee Point, in the Lake Macquarie region of NSW. We have a lot of Eucalypts around.
Just wondering if it’s something that’s going to attack the timber in my home?
Thanks very much
Signature: Regards.


Dear Heather,
This Longicorn is a Prionid in the subfamily Prioninae, and just last month we identified a submission (and corrected a misidentified submission from our archive) as
Agrianome spinicollis

Longicorns are members of the family Cerambycidae, and they are also known as Longhorned Borer Beetles because they have larvae that bore in wood, generally living or recently dead trees. 

Milled lumber is generally safe from infestation, however, it appears that your deck is surrounding a standing trunk.  Beetles in this family are usually host specific, and not general feeders.  According to the Queensland Museum site:  “This species is found in rainforest and open forest in eastern Australia.

It is common in Queensland and New South Wales and also occurs on Lord Howe Island. The larvae are huge white grubs found in rotten wood, especially dead Poinciana or fig trees. It is an important pest of pecan trees. The large adults sometimes blunder into house lights.”


Thank you,
we’ve relocated the beetle into the bush. The trunk (a palm) in the deck is not live, so I’m watching it for larvae. There are numerous holes in it, so it seems the beetle made a home there.
Have a nice Christmas and new year!

Letter 5 – Prionid Beetle

Large Bug In My Kitchen
I found this bug in my kitchen tonight and I was hoping you could help me figure out what it is and give me some information about it. I have never seen a bug like this before around here. I live in Buena Vista, Colorado. It is rather large. As you can see in the pictures, it is larger than the size of a quarter. It is about 1 1⁄4 inches long and the antennae are about another inch.

The pictures don’t show it very well, but the antennae and legs are very barbed (10 barbs on each antenna, 4 barbs on the front and middle legs, and 3 barbs on the back legs). Each of the legs ends with a double hook. My puppy thought this was a new toy for him which caught my attention. The bug was making a strange clicking type noise.

Not only when on its back but when it was walking around as well. It is entirely black looking at it from the top. Its belly is kind of a pale yellowish color. It almost appears bee-like because its shell seems to grow in an overlapping stripe-like pattern. When my husband tried to pick it up to take it outside, its back split into wings and tried to fly away.

The mouth area looks like it has small but sharp mandibles and four little finger-type things hanging down. As it was walking around, it was dragging these four fingers on the ground. I don’t know a whole lot about bugs and I hope the information I have given you is helpful.

If you have questions or would like more information, please let me know and I will do my best to provide some answers. Thank you for your time,
Stephanie Bailey

Hi Stephanie,
This is one of the Prionid Beetles. There are several species of Prionus listed in Colorado, but we are unsure which species you have. We will see if Eric Eaton can give us a species name when he returns. They are root and stump borers in the larval stages.

Letter 6 – Prionid Beetle is probably Palo Verde Borer

Can I get an ID bug man!
Sharon Hendricks
AFT 1521 Chapter President – Los Angeles City College
Trustee – CalSTRS


Dear Sharon,
Please use our standard form which can be accessed using the Ask What’s That Bug? link on the website.  The standard form requires certain information including the location of the sighting. 

Cronyism being what it is, we are happy we are able to assist in your identification, but future submissions to our personal email account should provide any details of the sighting that may help in the identification. 

If this sighting had occurred in Eagle Rock, it would have been noteworthy as this is some species of Prionid, a member of the Longicorn Borer Beetle subfamily Prioninae which is well represented on BugGuide

The poor quality of your image will not allow us to identify this Prionid to the species level, and if you would like that level of identification, we would strongly urge you to acquire a real camera and take a beginning digital photography class. 

While cellular telephones are wonderful in that they put image making capabilities in the hands of the masses, they are also contributing to the proliferation of bad imagery on the internet and to the general drop in quality of digital images. 

One should handle Prionids with caution, because though they are not poisonous, they do have strong mandibles that enable the adult beetle to chew its way through wood at the end of the pupation period when the adults emerge.  A bite could remove a chunk of skin and could easily result in a bleeding and painful wound.

Ed Note:  July 8, 2014
We just learned this sighting was in Arizona, and we suspect this might be a Palo Verde Borer

Letter 7 – Prionid Beetle Grubs

White Fat Grubs? Pics included!! Please respond ASAP!! Thanks!
While chopping wood in December, my dad stumbed upon 3 huge white grubs. I wrote you guys immediately but got no response. I wound up keeping them. When my dad gave them to me, they were out of their holes due to my dad cutting them (the holes) in half.

The next day, they had knawed back into the wood and covered the opening with what I’m guessing is a mix of saliva and wood shavings. Now as it is almost April, I was wondering what this grub (or insect) is before they pop out of their cacoons.

If I shake the wood slightly, I can feel them moving about. Characteristics: Off white VERY small head Black line running down back 6 small, almost nonexistant legs right behind head Thanks!! I hope they are some sort of beetle!!!

Hi Cammy,
Sorry we didn’t get to your first request. These are Cerambycid Beetle Grubs, or more specifically, Prionid Grubs. Not sure what species as you did not identify the tree nor your location. Your photo is awesome.

The grubs came out of a water oak (similar to a live oak) in Tampa Florida. The species name would be greatly appreciated.

Our best guess is Prionus imbricornus, the Tile Horned Prionus, which ranges in Florida and feeds on oak as well as other trees, shrubs, vines, and according to BugGuide, maize. This is a large and handsome beetle.

Letter 8 – Prionid Beetle, probably Palo Verde Root Borer

Identifying Giant “Beetle” in Tucson
July 6, 2010
Hello, this passed fourth of July, I was called in to carry children away from a giant scary bug. By the time I had gotten there, three children, all under the age of six were cautiously trying to get through the front door, which was guarded by an unknown watch-dog of a bug.

For kicks, would you be so kind as to identify it, and let them know how much danger, (If real or not hah) they were in?

It was about a little bigger than a pill bottle from top to bottom.
The bug itself was very docile if at times it moved fast, it was only to retreat from them and possibly light sources.

I’ve searched high and low and have not been able to identify our friend here. Apologies for only being able to provide one picture, it was hectic at the moment.
Thank you in advance.
Sincerely, Alejandro Incognito
Tucson, Arizona Southwestern USA

Palo Verde Root Borer we believe

Dear Alejandro,
Your photograph shows the general outline of a Prionid Root Borer in the subfamily Prioninae, but there isn’t enough detail to conclusively identify the species.  There are many species that can be found in Arizona, as browsing through the possibilities at BugGuide will reveal. 

Our best guess on this is the Palo Verde Root Borer, Derobrachus hoverei, as it most closely resembles the general structure and coloration discernible in your photograph. 

All of the Prionids have strong mandibles because after they metamorphose into adults, they need to chew out of the roots and stumps where they have spent their larval years feeding on wood pulp.  According to BugGuide:  “Adults attracted to lights.

Letter 9 – Prionid Borer and Bee-Mimic Flower Scarab from Slovakia

bugs from trip to Slovak Paradise
we have found these two beetles in Slovakia Paradise, could you please write some information about them, we are looking forward specially for information about this strange thing (cocoon,egg maybe) on back side of big beetle.

We spend over two hours observing this beetle, she brougth out and in this cocoon, but nothing happend at the end. Female fall asleep :-).

Hi Kris,
Your first beetle is one of the Prionid Borers in the Subfamily Prioninae, but we are not sure of the species. This female is swollen with eggs and the ovipositor was was being “unsheathed” into the position for egg laying.

The beetle would use the ovipositor to deposit eggs beneath the surface of bark on trees. Your second beetle is a Bee-Mimic Flower Scarab in the Tribe Trichiini.

Letter 10 – Prionid from Afghanistan

Subject: Afghan Beetle
Location: Eastern Afghanistan
August 18, 2016 1:20 am
I am currently deployed in Afghanistan and found this beetle outside our sleep tent. Just wandering if you could identify it and maybe give a little information about it. I’m more curious than anything and would like to pass on any helpful information to my guys here. Thanks.
Signature: CPT P

Prionid:  Prionus vartianorum
Prionid: Prionus vartianorum

Dear CPT P,
This is one of the Root Borers in the subfamily Prioninae.  We located the Afghanistan page of Prioninae of the World and it contains three species.  We believe your individual is a female
 Prionus vartianorum based on images on Prioninae of the World

No host plant is listed and the distribution is listed as solely Afghanistan, meaning the species may be endemic to Afghanistan.  Male Prionids are frequently attracted to lights, and females of some species are also attracted to lights. 

Virtual Collections has images of a male specimen, and the country listed is also just Afghanistan.  We believe it can go without saying that you should stay clear of the mandibles.  A large Prionid can easily draw blood should it bite a human.  

Prionid:  Prionus vartianorum
Prionid: Prionus vartianorum

Letter 11 – Prionid from Australia

Subject: What is this?
Location: Bobin, NSW,Australia
January 6, 2013 12:03 am
My brother caught this beetle last night which was quite large & it bit him several times, drawing blood.
We live on the Mid North Coast just out of Wingham NSW.
We would like to know what it is.
Signature: Jean Cameron


please attach a larger photo if possible.

Ed. Note:  We never received a response to our request.
Hi Jean,
This is a Prionid, a member of a subfamily among the Longhorned Borer Beetles.  We would really love a higher resolution file.  It looks similar to, but not exactly like the female
Rhipidocerus australasiae pictured on the Worldwide Cerambycidae Photo Gallery website.  It might be a greenish Poinciana Longicorn, Agrianome spinicollis, which is pictured on the Queensland Museum website.

Letter 12 – Prionid from Australia

Subject: What is this!?
Location: Buderim QLD 4556
November 30, 2016 6:00 pm
Hey there,
Found this little guy in my garage. Would say it would nearly be the size of my hand. Was HUGE!
His back looked like wood and he had six legs.
I live on the Sunshine Coast and it’s the first day of Summer here.
Thank you
Signature: Lilly


Dear Lilly,
This Root Borer in the subfamily Prioninae looks like
Agrianome spinicollis, and your submission is the third this year of this species.

Letter 13 – Prionid from Australia: Sceleocantha glabricollis

Subject: What’s this beetle?
Location: Australia, Queensland, Brisbane
November 23, 2015 3:05 pm
I found a really cool beetle in my bedroom but could not find out what type of beetle it was and am trying to get it identified. Also the bug has been released.
Signature: By Nic

Prionid:  Sceleocantha pilosicollis
Prionid: Sceleocantha glabricollis

Dear Nic,
This is a Longicorn in the family Cerambycidae, but more specifically it is a Prionid in the subfamily Prioninae.  At first we believed we had correctly identified the species as
Sceleocantha pilosicollis based on the image posted to Prioninae of the World

Additional research on Atlas of Living Australia only lists the species in West Australia, so we decided to search other members of the genus.  We learned on Atlas of Living Australia that Sceleocantha glabricollis is listed in Queensland and the rest of Eastern Australia, so we believe it may the the correct species. 

We would not rule out that we might be wrong, but the mandibles on the individual pictured on Prioninae of the World look quite similar to your specimen.  An image we located on FlickR is also a good visual match.

Prionid:  Sceleocantha pilosicollis
Prionid: Sceleocantha glabricollis

Letter 14 – Prionid from Brazil

Subject: coleopter ?
Location: Brazil Bahia
May 6, 2015 1:09 pm
Huge bug, at least 10cm long
Signature: ecotrancoso


Dear ecotrancoso,
You are correct that this is a beetle, and it is in the family Cerambycidae, the Longhorned Borer Beetles.  We are also quite confident that it is in the subfamily Prioninae, and according to BugGuide:  “world’s largest beetles are members of this subfamily.”

Letter 15 – Prionid from Honduras

Subject:  Beatle (looks like Paul)
Geographic location of the bug:  Venado Beach, Marcovia, Choluteca, Honduras
Date: 06/14/2019
Time: 04:33 PM EDT
Your letter to the bugman:  This guy came to pay a visit at the sea turtle observation center in the middle of the mangrove forest. It is approximately 7 cm long.
Thank you for your effort.
How you want your letter signed:  Enrik


Dear Enrik,
This is a Root Borer in the subfamily Prioninae.  It has some interesting features, but we are still having problems narrowing this to a species.  Coleoptera Neotropical has images of subfamily members found in Honduras.


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9 Comments. Leave new

  • Dolan Pinto
    May 23, 2014 9:54 am

    conognatha fisheri, acanthinodera cummigi y tauroceraste patagonicus.

    • Thank you so much for providing the identification information on this six year old posting. We will also tag the posting with all three families represented in the collection.

  • Ando Vaan (aka Mardikavana)
    May 7, 2015 10:23 pm

    Possibly Enoplocerus armillatus.

  • Can you eat them?

  • richard portman
    February 25, 2017 9:19 pm

    Those grubs are edible and tasty. Only a few times i have helped processs some trees from Cedar Mountain, southern Utah. We would find these and also “flathead” grubs(buprestid?).
    I could never eat them raw because of the goo factor. But they are delicious after you toast them for a minute or two. They taste like pine nuts. I would like to eat them again.

  • richard portman
    February 25, 2017 9:19 pm

    Those grubs are edible and tasty. Only a few times i have helped processs some trees from Cedar Mountain, southern Utah. We would find these and also “flathead” grubs(buprestid?).
    I could never eat them raw because of the goo factor. But they are delicious after you toast them for a minute or two. They taste like pine nuts. I would like to eat them again.

  • I found the same type grub in the stump of a tree that I was removing from my parents lawn. I believe it was an oak tree of some type – as I only had the stump of that particular tree and the other trees to go by…

    That grub was about 3 inches in length and is what my nightmares are made of.

    Give me wild carnivores or poisonous snakes over those creepy looking things any day

  • I found the same type grub in the stump of a tree that I was removing from my parents lawn. I believe it was an oak tree of some type – as I only had the stump of that particular tree and the other trees to go by…

    That grub was about 3 inches in length and is what my nightmares are made of.

    Give me wild carnivores or poisonous snakes over those creepy looking things any day


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