Brown Prionid: All You Need to Know About This Fascinating Beetle

The brown prionid, also known as Orthosoma brunneum, is a fascinating insect belonging to the longhorn beetle family.

Not only are they an exciting discovery for bug enthusiasts, but they also play a vital role in the ecosystem.

Brown prionids are known for their distinct elongated antennae, which make them easily identifiable.

These beetles are primarily found in the wooded areas of North America, where they contribute to the natural process of breaking down and recycling dead wood material.

In their natural habitat, brown prionids have certain advantages and disadvantages.

These beetles assist in decomposing wood, providing essential nutrients to the soil. However, on the downside, they can sometimes damage healthy trees if their population increases uncontrollably.

Brown Prionid: Basic Information

Classification and Scientific Name

The Brown Prionid (Orthosoma brunneum) belongs to the order Coleoptera and the family Cerambycidae. Specifically, it falls under:

  • Kingdom: Animalia
  • Phylum: Arthropoda
  • Class: Insecta
  • Order: Coleoptera
  • Family: Cerambycidae
  • Subfamily: Prioninae
  • Tribe: Prionini

Physical Description

The Brown Prionid is known for its distinct antennae. These beetles have:

  • Brown coloration
  • Elongated body shape
  • Body length: 20-50mm
  • Wing patterns: Brown with variable markings

Physical features of the Brown Prionid include:

  • Long and straight antennae
  • Robust body structure
  • Its mandibles are Large and curved

The bug uses its large mandibles for fighting and mating. Their antennae are especially noticeable due to their length and segmentation.

Compared to other beetles in the Cerambycidae family, the Brown Prionid’s antennae are relatively shorter.

Distinctive Sound

The Brown Prionid is known for its squeaking sound. This sound is produced using a method called stridulation:

  • Rubbing its wings against its abdomen
  • Utilized for communication and attracting mates

Life Cycle and Behavior

Eggs and Larvae

The life cycle of the brown prionid begins with the female laying eggs. These eggs are typically laid near decaying wood or roots of trees, like oaks.

Upon hatching, the larvae emerge and start feeding on roots and decaying wood. Some key characteristics of the larvae are:

  • Creamy white color
  • C-shaped body
  • Well-developed mandibles

Larvae prefer feeding on the roots of various trees and shrubs, providing them with essential nutrients.

Pupa and Adult

After reaching a certain size, the larvae undergo pupation and transform into pupae.

Pupation occurs mainly in the soil, near the food source. Key features of the brown prionid pupa include:

  • Exarate (free) appendages
  • Inactive and immobile stage

The pupal stage is followed by the emergence of adults. Adult brown prionid beetles are nocturnal, meaning they are active during the night.

Some features of the adult brown prionid include:

  • Brownish-black color
  • Robust body, measuring up to 2 inches in length
  • Attracted to light sources
Life Stage Characteristics
Egg Laid near decaying wood or roots of trees, like oaks
Larva Creamy white, C-shaped, feed on roots and decaying wood
Pupa Exarate appendages, inactive, mainly in the soil near a food source
Adult Brownish-black, robust body, nocturnal, attracted to light sources

The typical lifespan of a brown prionid beetle ranges from one to two years, depending on the availability of food and environmental conditions.

Habitat and Distribution

Native Range

The brown prionid (Orthosoma brunneum) is a native species primarily found in North America. Its range extends from Maryland in the north to Howard County in the south

This beetle thrives in areas with decaying wood, especially moist and rotting wood, which is essential for its growth and development.


Brown prionids prefer habitats with abundant decaying wood, which they use for shelter, reproduction, and as a source of food. Some key habitat features include:

  • Moist: Brown prionids require moisture to survive, and they can be found residing in damp and decaying wood.
  • Decaying Wood: They are commonly found in environments with ample decaying wood, such as forests and woodlands.

Some examples of their preferred habitats include:

  1. Forests with rotting logs
  2. Old lumber piles
  3. Tree stumps in various stages of decay

Brown prionids can sometimes be found in residential areas if there is a sufficient abundance of decaying wood.

The brown prionid’s native habitat is essential for its survival, and maintaining a healthy ecosystem with decaying wood ensures their continued existence.

Diet, Damage, and Predators

Feeding Habits

The brown prionid beetle feeds primarily on decaying wood, plant roots, and sometimes bark. It is commonly found in forests and wooded areas.

  • Diet includes:
    • Decaying wood
    • Plant roots
    • Bark

Potential Harm

Brown prionid beetles can cause minor damage to trees and plants due to their feeding habits. However, they are not considered a significant threat to forests or agriculture.

  • Minor damage to:
    • Trees
    • Plants

Natural Predators

Brown prionid beetles have several natural predators, which help control their population in the ecosystem.

  • Predators include:
    • Birds
    • Small mammals
    • Flies

For instance, certain fly species lay eggs in the larval stage of the brown prionid beetles, consuming and limiting their population growth.

Human Interaction

The Brown Prionid beetle, while primarily a dweller of forests and wooded areas, occasionally comes into contact with humans, especially in regions where their habitats overlap with populated areas. Here’s a closer look at these interactions:

Pest or Friend?

Generally, Brown Prionids are not considered harmful pests to humans. They don’t bite or sting, and their primary diet consists of decaying wood and plant roots.

However, in areas where they are abundant, their larvae might cause minor damage to tree roots or garden plants.

On the positive side, by feeding on decaying wood, they play a role in the natural decomposition process, recycling nutrients back into the soil.

Attraction to Lights

Like many beetle species, Brown Prionids are attracted to artificial lights. It’s not uncommon for residents in areas with a significant Brown Prionid population to find these beetles buzzing around porch lights or street lamps during the night.

This can sometimes lead to accidental home invasions, especially during warmer months when windows and doors are frequently left open.


The brown prionid, scientifically termed as Orthosoma brunneum, is a captivating member of the longhorn beetle family, predominantly found in North America’s wooded regions.

Recognizable by its elongated antennae and brown hue, this beetle plays a pivotal role in the ecosystem by aiding in the decomposition of dead wood.

While they do have a penchant for decaying wood, plant roots, and bark, their impact on trees and plants is relatively minor. However, their presence can sometimes be a concern if their population surges uncontrollably.

By understanding their life cycle, habitat preferences, and behavior, we can appreciate their role in nature and manage their presence effectively.

Reader Emails

Over the years, our website, 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 – Tile Horned Prionid

palmetto-like bug with fuzzy antennae
Jul 10, 2009
palmetto-like bug with fuzzy antennae
These interesting critters parked themselves on our door after a rainy day. They were bigger than the roaches we have here in the south. We haven’t seen them since that night. We were wondering what these rare insects are called.
Thanks from Clemson
South Carolina

Tile Horned Prionus
Tile Horned Prionus

Hi Clemson
This is one of the Root Borers in the genus Prionus, the Tile Horned Prionus, Prionus imbricornis.  You may read more about this species and its relatives on BugGuide.

Letter 2 – Brown Prionid

Subject: American Cockroach Poser
Location: Dobbs Ferry, New York
July 15, 2014 6:56 pm
So the other night (low 80 degree night, pretty humid, on July 14th) I was sleeping in my basement when I woke up to an insect crawling over my face and on my body. I proceeded to jump out of bed, scream and run to my couch (I’m not a huge bug fan) about 30 seconds later the bug crawled across the bed and took flight (clumsy flight) towards a different part of the room.

We’ve been living in Westchester, NY (about 17 miles north of new york city) for over 17 years and have never seen a cockroach, our basement is pretty dry as far as basements go and we keep it pretty clean, however, there are a number of american cockroaches in my local middle and high school.

When inspecting the bug after we had caught it a day later I noticed its antennae did not match the american cockroach. Is this a beetle? Or possibly another species of bug? I’m extremely curious and confused, any information would be greatly appreciated.
Signature: Clara Winder

Brown Prionid
Brown Prionid

Dear Clara,
This impressive beetle is a Brown Prionid.  Though they are not considered dangerous, they have strong mandibles that may give a painful bite, possibly even drawing blood, if they are carelessly handled.

Letter 3 – Brown Prionid

Long, sedentary beetle in NJ
July 4, 2010
I trolled BugGuide with no success. This critter, with a length of about 3 or 4cm, stayed stationary all evening. It was about 70F with moderate humidity on a clear night.
Thanks, and happy 4th!
Greg in NJ
Central NJ

Brown Prionid

Good Morning Greg,
Your beetle is the Brown Prionid,
Orthosoma brunneum, and it can be recognized, according to BugGuide, by “Light brown, sides of elytra parallel. 11-segmented antennae, rounded, never flattened.

Letter 4 – Brown Prionid

Subject: Huge Beetle Found! Invasive or Not?
Location: Eastern United States, DE
July 22, 2014 11:06 pm
Hello! I’ve got a bug on my hands – well, in a jar – and I don’t know what to do with it.
I have lived in this area for 20+ years and am an avid outdoorswoman. This critter was trying to get into my house through the window screen, and I’d like some expert help figuring out just what it is.

Because I’ve never, ever seen it before.
This beetle is large, nearly two inches long, with a slender body about half an inch wide. It’s a rusty reddish brown color, with black mandibles and antennae about an inch long. There are no discernible markings.

I’ve confirmed that it is not a cockroach of any variety, and if it didn’t have terrifying looking mandibles I’d be picking it up to take better photos.
I’d like to know if it’s a type of boring beetle or not, so I can know if it’s invasive or not. I’ve never seen it before and it’s rather concerning to see something this…enormous on my window trying to nibble the screen.

Any info pointing me in the right direction would be awesome. 🙂
Signature: ~ Kat of the Coast

Brown Prionid
Brown Prionid

Dear Kat of the Coast,
Root Borers in the family Prioninae are quite impressive beetles and there are several native species found in Delaware, even if they have managed to avoid detection by you in the past. 

This is a Brown Prionid, Orthosoma brunneum, and you are wise to avoid its mandibles.  The grubs of Root Borers live feeding on wood for several years and the mandibles of the adults need to be strong enough to chew their way to the surface once metamorphosis is complete. 

We suspect this individual was attracted to light, and that is why you discovered it on your screen.  See BugGuide for additional information on the Brown Prionid.  We would urge you to release your captive Brown Prionid.

Letter 5 – Brown Prionid

Subject:  What is this?
Geographic location of the bug:  North Carolina
Date: 06/27/2019
Time: 01:33 PM EDT
Your letter to the bugman:  What is this???
How you want your letter signed:  Signed,

Brown Prionid

This is one of the large Prionid Beetles that appear each summer in many parts of North America.  Your individual is a Brown Prionid, Orthosoma brunneum

Letter 6 – Brown Prionid

Subject:  Large Long Brown Beetle
Geographic location of the bug:  Georgia
Date: 07/03/2019
Time: 11:19 PM EDT
Your letter to the bugman:  Saw this large guy (over 2 inches long!) chilling on our house. I tried googling him but there are so many generic brown beetles it’s hard to narrow him down. Any thoughts?
How you want your letter signed:  Vika

Brown Prionid

Dear Vika,
The Brown Prionid is a relatively common summer identification request from the eastern parts of North America.

Letter 7 – Prionid from Puerto Rico

Subject: Type of beetle?
Location: Dorado, Puerto Rico
May 18, 2014 3:37 pm
We found this beetle on the wall od our terrace, what kind is it?
Signature: Pili

Prionid or Root Borer
Prionid or Root Borer

Dear Pili,
Your beetle reminds us of a North American Prionid known as the Hardwood Stump Borer,
Mallodon dasystomus, so we tried to search for Puerto Rican species, and we found a reference on Prioninae of the World to a Puerto Rican species, Nothopleurus maxillosus, formerly known as Mallodon maxillosum.

An image of a Brazilian relative, Nothopleurus lobigenis, that we found on Cerambycidae Species looks very similar to your individual.  Continued searching brought us to an image on the Worldwide Cerambycidae Photo Gallery that looks very close to your image and it is identified as Hovorodon bituberculatum.  We would not rule out Stenodontes exsertus also found on the Worldwide Cerabmycidae Photo Gallery.

Letter 8 – Brown Prionid

Subject: Unknown Beetle?
Location: Lebanon, Maine
August 4, 2014 5:43 pm
Hello, I was searching in my basement for old things and I came across this big guy. My basement is rather moist from the humidity and has a lot of old cardboard boxes around.

This creature is about one inch in length excluding the antennas and looks around 2 millimeters in width. It has six legs and a nice little jaw bone look that normal beetles have. Looks along the lines of a soldier beetle but different colors. I’d appreciate it if you could help me out here. I’d be pretty freaked if it were a cockroach.
Signature: Yours truly.

Brown Prionid
Brown Prionid

Dear Yours truly,
Images of Brown Prionids,
Orthosoma brunneum, like the one you submitted, continue to pour into our site for identification.  Though they are not considered dangerous, Brown Prionids, like many other members of the Longhorned Borer family Cerambycidae, have very powerful mandibles and they might draw blood from a bite if carelessly handled.

Letter 9 – Prionid from Zimbabwe

Subject: Longhorn beetle
Location: Philadelphia, Harare, Zimbabwe
January 31, 2017 6:14 am
I have narrowed down the identity of this beetle to Tithoes Confinus or Tithoes Maculatus. What do you think?
Signature: Majotso

Prionid: Some species of Tithoes

Dear Majotso,
We have several Prionids from Africa in our archives that we have identified as
Tithoes confinus, but we would always defer to true experts when it comes to determining the exact species. 

Many times members of the same genus require close examination to determine an exact identity and we just do not possess the necessary qualifications to make that determination.  Perhaps one of our readers will be able to provide more specifics.  This posting from our archives has some information on distinguishing T. confinus from T. maculatus

ISpot has many postings from the genus, and not a single one is identified as T. maculatus, and several are identified as T. does have an image of a pair of T. maculatus, and the range is listed as “Angola Bénin Burkina Faso Cameroun Centrafrique Côte d’Ivoire Gabon Gambie Guinée BIssau Mali Niger Nigeria Rwanda Sénégal Soudan Tchad Togo” and not Zimbabwe.

Which Tithoes species???

Thank you Daniel,
I posted this pic on NatureWatch NZ and got feedback from Jacob and fubr as being T. maculatus frontalis which I now agree with.


Letter 10 – Prionid from South Africa may be Anthracocentrus capensis

Subject: BIG bug!
Location: Gamkaskloof (Swartberg), Western Cape
February 26, 2017 9:18 am
What exactly is this large beetle with big pincers please?
Signature: No preference


Dear George,
This is a Root Borer in the subfamily Prioninae, and we believe that based on images posted to iSpot,
Anthracocentrus capensis is a likely species identification.  A note on iSpot states: 

“In case you may miss some scale in this picture, this is an enormous beetle in excess of 80mm long, and one of the very largest beetles in southern Africa. The individual here is a female; the male bears even considerably longer mandibles (“jaws”).”  There is a nice comparison image showing the male and female on

Letter 11 – Brown Prionid

Geographic location of the bug:  New Portland Maine
Date: 07/26/2018
Time: 11:02 AM EDT
Your letter to the bugman:  Hi there! I was hoping you could give me a confirmation as to what in God’s name this guy is!!?? I saw it scurrying across the kitchen floor and almost lost my mind as initially I thought it was a cockroach but it didn’t move as fast and has a different body shape (this guy is more rounded, kind of shell-like and the wings are side by side not folded across the back like a roach).

I was able to put a paper cup over it and scoured the internet to find out what this  is.  I came across a click beetle, so turned it on it’s back to see if it made a “clicking” sound when it flipped back…it couldn’t flip over…it made a TON of noise though…like chirping/squeaking.

I rolled it back and covered it again.  Looked more and really I couldn’t find anything that matched, THEN  I  and found your site!  It’s FANTASTIC!  Within a few seconds I saw a picture of what I think I have here..  Brown Prionid. ..So other than a confirmation, I want to know if it’s a benign being and I should let it go on it’s way (outside of course) or a problematic intruder and  I should burn the house down and nuke the yard?  Oh, one more thing….are they capable of swimming?
Thanks a bunch!
How you want your letter signed:  Elise in Maine

Brown Prionid

Dear Elise,
Thanks for the compliment.  You are correct.  This is a Brown Prionid, and in our opinion, you should release it and not “burn the house down and nuke the yard,”  though that does make us chuckle and it reminds us of a response we once gave a reader, that “nothing short of a nuclear bomb will rid your property of all your dreaded insects.” 

According to BugGuide:  “Breeds in poles, roots(?) in contact with wet ground” meaning the larvae develop in rotting wood.  To the best of our knowledge, they do not infest homes nor do they trouble healthy trees, so in our opinion, they are benign.  Furthermore, these large beetles are a very nutritious source of food for many forms of wildlife.  They do not swim.

Brown Prionid

Letter 12 – Mating Brown Prionids

a photo for bug love?
Bug man,
You have helped me on many a quandry as to what I have discovered on porch screens late at night at my home. Recently I believe I’ve found a bug that does not regularly end up in Northeast Missouri.

They looked like mating Palo Verde Root Borers and were they ever big! I think the only reason I was able to find them was that they had stopped to get friendly in a lighted window. Sincerely,
Jessica Martin

Hi Jessica,
These look to us like mating Brown Prionids, Orthosoma brunneum. There are photos on BugGuide to match, and they are found in Missouri.

Letter 13 – Brown Prionid

Orthosoma brunneum?
We found three of these around our home this evening, they are attracted to light and pretty much unafraid even when touched. They also shiver and make a strange sound something like a cricket but more unique.

My wife had a brief meltdown when she went online and saw a photo of an American cockroach – she was convinced that’s what we had and was ready to move! I had to become an amateur entomologist tonight using my camera, your site and other online resources. I think I can put her mind at ease- do you agree it is an Orthosoma brunneum?

This guy is 4.25 cm long and currently living in a jar with a gumdrop courtesy of my 2 1/2 year old daughter. (She named him buggy.) If you concur we’ll grant him compassionate release on the grounds that he’s no roach. Let us know! Great site, thanks for all your hard work, Sincerely,
Joe, Heidi and Hope in Hawthorne, NJ

Hi Joe, Heidi and Hope,
Your identification on the Brown Prionid, Orthosoma brunneum, is correct.

Letter 14 – Brown Prionid

what is it
I was just looking thru your site to try and identify this beetle I found tonight. It looks like the California long horn beetle. But I am in NH on vacation. Should I not release this insect. Is it not native to this area. I am sending the picture I took, but not very good since the beetle is in a vile for safe keeping until I hear that it is safe to release it.

We must confess that we were sure you had one of the Long-Horned Borer Beetles, but we were unsure of the genus and species. We asked Eric Eaton to try to clarify some identification points for us, which he did. However, in identifying your beetle, we now have an entirely new genus to consider.

Here is Eric’s response: “This appears to be a female Orthosoma brunneum, the Brown Prionid. Just what you needed, eh, another critter to get confused by:-) Ergates are large, western mountains mostly, with FINE teeth on the edge thorax. Derobrachus are HUGE, almost exclusively southwestern (though range throughout the souther tier of states I am told).

Prionus usually tend to be very squat, males with very thick antennae (almost comb-like or dentate in some species). An overall more robust critter than the others. Orthosoma is the most slender of all, and always a bright brown in color. Hope that helps, but getting Doug Yanega’s book on northeast longhorns would be your best bet (less than $20). Eric “

Letter 15 – Brown Prionid

Large Beetle found
Hi there, My wife found this beetle today (7/18/06) in the basement bathroom of our home in Rockfall, CT. It is the largest beetle (approximately 1 3⁄4” long) I have seen in or around here before.

We are just curious as to what it is called. It looks similar to a Paulo (?) root beetle but since we are in CT I’m not sure if it is. Well I hope you like the pictures! Thanks!

Hi Aaron,
We believe this to be a Brown Prionid, Orthosoma brunneum, which has 11 antenna segments. It breeds in poles and roots in contact with wet ground. It was probably attracted to lights in your bathroom.

Letter 16 – Brown Prionid

bug question, duh
What the heck is the big guy?

Hi Molly,
Labeling your photo “wedding and grad party” isn’t really what we had in mind when we put a request on our homepage for readers to provide us with location information on their submissions.

We prefer global location information since that is much more useful considering letters come to us from all over the world. The “duh” in your subject heading leads us to believe there might have been some intoxication involved at the wedding and graduation party, and we are thrilled there is an auto focus feature on modern cameras allowing even operators with a high blood alcohol level to take crisp clear photos like yours.

We hope the hangover has subsided. This is a Brown Prionid, Orthosoma brunneum. They are attracted to lights, which is probably the reason the small moth is hitch-hiking. They are found in moist locations in eastern North America. Eggs are laid in wood in contact with wet ground, including poles.

Letter 17 – Brown Prionid

I know you are busy but please help me!!!!!
Good morning,
Let me first say that I love your site and use it often. You recently saved the lives of the Golden Digger Wasps that are busy working in our yard. Now our two year old can play right next to there holes and we really don’t worry all that much. You have been very helpful to us and the little critters that live with us.

This morning though, I have become VERY uptight about somebody that was sitting in an empty wineglass on my counter. Please tell me this is NOT a roach, cause if it is, I am abandoning my home immediately.

He is huge, and quite quiet, not at all what I would imagine a roach would behave like.Can you ease my fears, please… Thanks so much,
Carla in Connecticut

Fear Not Carla,
This is not a roach. It is a Brown Prionid, Orthosoma brunneum. The larvae are wood borers and are usually found in poles and wood that is in contact with wet ground. We are also happy to hear your Golden Digger Wasps are alive and well.

Letter 18 – Brown Prionid

Some sort of beetle?
We just found your site…very cool! We are kind of bug people so it’s fun to see. I found this on the screen of the kitchen window. The light in the kitchen was on but I turned it off for the photo. It was around 10pm. Thanks,

Hi Shadley,
This is a Brown Prionid, Orthosoma brunneum. This is one of the Longhorned Borer Beetles and the grubs feed in poles and roots that are in contact with wet ground.

Letter 19 – Brown Prionid

Orthosoma brunneum
I cam across your web site while trying to identify a caterpillar and fell in love. I check out your site almost every day I just can’t get enough of all the great pics and info. With my 7year old daughter being a bug fanatic we have had quite a few bug pet that we keep for a couple of days to watch and then let them go.

So when ever we find a new one we check here first. Anyway in search of identification on this one. I found him on my front porch at night by the light. We live in southwest PA. I believe it to be an Orthosoma brunneum. The one I found on your site you were not sure because of the pic so I hope my picture will help. Keep up the good work I’ll always be a viewer. Thanks

Hi Mike,
You are correct. Orthosoma burnneum is commonly called the Brown Prionid. We are thrilled to hear you and your daughter get such enjoyment from our website.

Letter 20 – Brown Prionid

Thu, Oct 9, 2008 at 4:18 AM
Hey Bugman, I love your site. It has been a favorite since we moved into our NJ home 4 yrs ago. I know you are quite busy, but I think this is a brown long horn beetle. Could you please tell me if is, and how menacing they are to our trees & gardens. I have noticed a number of giant stag horns also lately. Thank you in advance.
Cindy Lea
Plainfield, NJ

Brown Prionid
Brown Prionid

Hi Cindy,
You are correct, but more specifically, this is a Brown Prionid, Orthosoma brunneum. According to BugGuide, it “Breeds in poles, roots(?) in contact with wet ground. ” We would presume that the species is not a problem for healthy trees, but that it may become a problem if it breeds in support poles that are in contact with the ground. We doubt it is plentiful enough to cause you any concern.

Letter 21 – Brown Prionid

Location:  South-central PA
July 26, 2010 8:31 am
I found this beetle? inside my house late at night, 7-25-2010. I live in a rural area with many trees and a stream. He is at least 30mm, mostly brown and has points off body, right behind the head. There are little ”feelers” around the mouth. Clear wingtips are sticking out at the end. I thank you for taking the time to look at my request.
Bethanne Schott

Brown Prionid

Hi Bethanne,
Your beetle is a Brown Prionid,
Orthosoma brunneum, and it is found in the Eastern portion of North America.  BugGuide reports is as far west as Texas and indicates it “Breeds in poles, roots(?) in contact with wet ground.

Letter 22 – Brown Prionid

California Root Borer???
Location:  Northeastern United States (Ohio, USA)
August 13, 2010 9:00 pm
Dear Bugman: This bug was on our screenhouse while we were camping in our home state of Ohio in the middle of July. From your photos it resembles the California Root Borer but we are a long way from there. This one also appears longer.

This was a big bugger about 2 1/4 inches long. At first glance before the pic was took it looked like it had silver drops for eyes along with the gold bands and we wondered if it had been eating radiation. I’ve seen many bugs in my day but not like this one.
Kathy (Ohio)

Brown Prionid

Hi Kathy,
For some reason, your entire digital file didn’t properly download and there are missing pixels that have cropped into this Brown Prionid’s abdomen.  Your observation that it looked similar to a California Root Borer is quite astute as they are both in the same tribe, Prionini. 

Your Brown Prionid is Orthosoma burnneum, and according to BugGuide it is found in moist forested areas from May to November.  Though there is an extended sighting period noted, most of the submissions of Giant Root Borers in the subfamily Prioninae, humorously referred to on BugGuide as “The Really Big Borers” come in July and August.

Hello Daniel,
Thanks for your quick response and thorough information. I’m sorry about the cropped pic. My son took the pic and IM’ed it to me. If I can get a better one from him, I will email it to you. My brother and I are very interested in bugs.

We have said that since our weather here in Ohio has been very hot and humid this summer and likened to the southern US climate that we may start to see insects indigenous to that area migrating up north. We feel this is an interesting concept and worth the watch. If I notice this then I will email you the info.

Kathy C. Seeman

Letter 23 – Brown Prionid

longhorn borer?
Location: alamo, tn.
June 22, 2011 11:26 am
If you have the time will you please give me the exact name of this beauty. I was sooo pleased to see him this morning. He was 2 inches in size. Thank you, beth light
Signature: beth light

Brown Prionid

Dear Beth,
We cannot help but to be overjoyed to read of your enthusiasm at this sighting and to read that you consider this magnificent beetle to be a “beauty”, but we couldn’t agree more.  It is a Brown Prionid,
Orthosoma brunneum, and according to BugGuide it is found in moist forests in Eastern North America (Bugguide does indicate sightings in Texas) and it breeds in rotting wood found in contact with the ground.  Prionids are a subfamily of the Longhorned Borers.

Letter 24 – Brown Prionid

Orthosoma Brunneum-very cool looking beetle!
Location: Seymour, Tennessee (just south of Knoxville)
June 26, 2011 10:49 pm
Hello Bugman,
I know Brown Prionids like the one in this photo are pretty common, but if I do say so myself, this photo turned out so good and they look so cool, so I thought I’d share it with you. I hope you enjoy it! Thanks for all you do. You are awesome and I love coming back to your sight multiple times each day!
Signature: Michael Davis

Brown Prionid

Dear Michael,
Thanks for your compliment.  While we are more inclined to post rare and under-represented species on our site, we also love posting beautiful images of more common insects. 

The season is upon us for Prionid sightings, and the Brown Prionid is one of the most beautiful representatives from the group.  We also love your photograph.  The colors are stunning, and the cool green of the wall is a perfect background for the rich brown color of the beetle.

Letter 25 – Brown Prionid

Beetle in Vermont
Location: Saxtons River, VT
July 27, 2011 10:34 pm
Hi Daniel,
Wondering if you can identify this beetle? It was on my screen door tonight, in southeast Vermont. It was about 1.5” in length. Thanks!
Signature: K L Thalin

Brown Prionid

Dear K L Thalin,
This beautiful beetle is a Brown Prionid,
Orthosoma brunneum, and it is one of a group known collectively at Root Borers.  If you would like to see more about this stunning creature, you can check out BugGuide.

Letter 26 – Brown Prionid

What kind of beetle is this?
Location: Granville, OH
August 15, 2011 11:44 am
Found on our deck in Ohio — bigger than other beetles we’ve seen.
Signature: Lisa Kelleher

Brown Prionid

Dear Lisa,
This magnificent beetle is known as a Brown Prionid,
Orthosoma brunneum, and we have received a few identification requests for it this season.  According to BugGuide, it:  “Breeds in poles, roots(?) in contact with wet ground.”

Letter 27 – Brown Prionid

Subject: b
Location: Staten Island, NY
June 10, 2013 5:04 pm
Hi! I was hoping someone could positively identify this bug, and maybe provide some info on it. I think it might be a pine sawyer, but I’m not sure.
I found it inside my house in Staten Island, NY just as a long winter was finally ending. This was also after Hurricane Sandy hit our area pretty hard and it started to get cold…..
Is this a common insect around here? I’ve never seen one like it before.
Signature: -b

Brown Prionid
Brown Prionid

Dear b,
Like the Sawyers, this is a Longhorned Borer, but unlike the Sawyers, it is in the subfamily Prioninae, and we believe it is the Brown Prionid, Orthosoma brunneum.  Prionids are Root Borers that spend their larval stage “in poles, roots(?) in contact with wet ground” according to BugGuide, which also indicates: 

“Adults come to bait, so presumably take some rotting fruit, sap?”  They are a wide ranging eastern species and they are not considered to be rare, though they might be absent in some portions of their range due to a shortage of available food.

Brown Prionid
Brown Prionid

Hi Daniel!
Thank you for the response and information!

Letter 28 – Brown Prionid

Subject: what is this?!
Location: philadelphia, pa
July 12, 2013 12:34 am
And idea what this is? Found it flying around my bedroom.
Signature: needs help!!

Brown Prionid
Brown Prionid

This is a Brown Prionid, Orthosoma burnneum, and adults are active during the summer months.  They are sometimes attracted to lights, and we suspect that is the reason it flew into your bedroom.

Brown Prionid
Brown Prionid

Letter 29 – Brown Prionid

Subject: bug
Location: western pa
July 26, 2013 10:36 pm
Found this bug outside on a wall on 7-26-13 temp was about 70 degrees
Signature: janet

Brown Prionid
Brown Prionid

Hi Janet,
This is a Brown Prionid,
Orthosoma brunneum, and according to BugGuide, it:  “Breeds in poles, roots(?) in contact with wet ground.”

Letter 30 – Brown Prionid

Subject: Long-horned Beetle
Location: Central Massachusetts
July 7, 2014 10:41 pm
I saw this enormous thing late at night on my bean plants. It does not appear to have the markings or coloration of the Asian Longhorned beetle or the whitespotted sawyer beetle. It flew away while I was photographing it and landed too high for me to get better photos. It’s at least three inches long, not including it’s extremely long antennae.
Signature: Ellen P.

Brown Prionid

Hi Ellen,
This is one of the Longicorns in the subfamily Prioninae, but we are uncertain of the species because of the camera angle.  Our best guess is that this is a Brown Prionid,
Orthosoma brunneum.

Letter 31 – Brown Prionid

Subject: beetle on screen door
Location: Princeton, NJ
July 25, 2014 7:21 pm
I found this guy hanging on my screen door in Princeton, NJ last night. Never seen one like it before! Some type of beetle, obviously. It’s about an inch and a half long, reddish-brown, with a orange stomach. Got any ideas?
Signature: Lynn

Brown Prionid
Brown Prionid

Dear Lynn,
It seems we have fielded more than the usual number of Brown Prionid,
Orthosoma brunneum, identifications this summer.

Letter 32 – Brown Prionid

Subject: brown beetle?
Location: currently in IL, but not where it came from
July 27, 2014 10:40 am
We just returned from a two week trip that took us through Illinois, Indiana, Ohio, Pennsylvania, Maryland, Virginia, North Carolina, West Virginia, and Kentucky. It was hot and humid, with a few big storms that rolled through. When we got home, this bug was in our van.

It is about two inches in length, not including the antennae, which add another inch (if pulled straight). It flies and seems attracted to light. Wondering what it is. We live in central IL and aren’t comfortable with just letting it go, without knowing if it’ll cause harm.
If we can’t let it go back into the wild, then we need to know what it is so we can care for it. Thank you!
Signature: Heather

Brown Prionid
Brown Prionid

Dear Heather,
We have received more than the usual number of Brown Prionid,
Orthosoma brunneum, identification requests from eastern North America this summer.  According to BugGuide, Illinois is well within the sighting range of the species, which is native.  Local populations may vary from place to place within the range.

Letter 33 – Brown Prionid

Subject: What is this?
Location: Central New Jersey
August 3, 2014 8:13 pm
We found this bug in our house upon returning from vacation. It was just lying on the floor in our family room. We were glad that it was already dead and we weren’t here when it entered.

Neighbors have mentioned finding similar ones in the neighborhood, but no one seems to have seen them before this year. Seems to look like a lot of other beetles out there, but the tail stinger is throwing us off.
Signature: Jeanette

Brown Prionid
Brown Prionid

Hi Jeanette,
It seems like this year we have gotten a few more reports of Brown Prionids,
Orthosoma brunneum, than we have in previous years, but mid summer is the peak time for sightings of this species and its relatives.  What you have mistaken for a stinger is the ovipositor of the female, an organ used to lay eggs.

Letter 34 – Brown Prionid

Subject: Caught by our cat
Location: NW Wisconsin
August 12, 2014 2:53 pm
This bug was hiding in the sunroom INSIDE the house, cornered by the cat. The bug was aggressive and actually squeaked when confronted. Very large, two inch range. Sorry, the dead body is gone. But, we have a picture. Looking forward to any guesses. Thanks, Keith
Signature: Keith

Brown Prionid
Brown Prionid

Hi Keith,
This impressive beetle is a Brown Prionid,
Orthosoma brunneum, and while we tend to get a few submissions of Brown Prionids each summer, we have had a significantly greater numer this summer. 

The larvae are wood borers and according to BugGuide:  “Breeds in poles, roots(?) in contact with wet ground.”  We suspect this individual was attracted to your house because of lights.

Letter 35 – Brown Prionid

Subject: Roach
Location: Pennsylvania
July 13, 2015 2:26 pm
Hello. I saw this bug on the outside of glass French door the other morning. Now I found him or his buddy under the wheel of the grill on deck, which is located a short distance from French doors. I am watching him now he’s slowly moving back under the grill wheel. Boy I hope it’s not a roach! He’s about 2 inches long
Signature: Heather

Brown Prionid
Brown Prionid

Dear Heather,
This is not a roach.  This impressive beetle is a Brown Prionid,
Orthosoma brunneum.

Letter 36 – Brown Prionid

Subject: Brown Prionus Beetle?
Location: Troy, VA
July 9, 2016 8:56 am
This large and impressive beetle was on my screen last night. I’m guessing it’s a prionus beetle.
Thanks for your help.
Signature: Grace Pedalino

Brown Prionid
Brown Prionid

Dear Grace,
This is NOT a Brown Prionus, but it is a Brown Prionid, and hopefully we will be able to properly explain the difference.  All living organisms on our planet are classified by an increasingly more specific categorization, beginning with the Kingdom, which in this case is Animal, and ending with a species designation of a lower case name following the genus, and forming the binomial that ensures that each creature is recognized as a distinct species worldwide. 

It should be noted that a subspecies name may follow the species name, in which case the subspecies will have a trinomial, three-part name.  Your beetle’s binomial genus/species name is Orthosoma brunneum and it is commonly known as the Brown Prionid. 

A Prionid is a Longhorned Borer Beetle that is classified in the subfamily Prioninae, and that subfamily also includes beetles in the genus Prionus.  So the genus Prionus and the genus Orthosoma are both in the subfamily Prioninae and their members collectively can be called the Prionids. 

Letter 37 – Brown Prionid

Subject: What is this??
Location: Western PA
July 17, 2016 10:50 am
Found this bug on the side of my couch and cannot identify it. It’s reddish brown in color and about 3 inches long. From the western Pennsylvania area. Can you help?
Signature: Nicole

Brown Prionid
Brown Prionid

Dear Nicole,
We suspect this Brown Prionid entered your home after being attracted to lights.

Letter 38 – Brown Prionid

Subject: This doesn’t look like a PA native
Location: Pennsylvania
July 22, 2016 9:46 pm
About 1-1/2″ long. We didn’t spend much time together, he was quickly relocated to the great outdoors. This is in Pennsylvania.
Signature: Christine

Brown Prionid
Brown Prionid

Dear Christine,
The Brown Prionid,
Orthosoma brunneum, is a native species in Pennsylvania.

Letter 39 – Brown Prionids

Subject: beatle/cockroach looking monstrosity
Location: northern new jersey suburbs
July 25, 2016 1:10 pm
Dear bugman,
Hello old sport was wondering if you could help me I.d. this scoundrel. Only have seen them at night, mostly seen flying into my garage from the outside. My brother says they fly sort of upright rather than parallel to the ground. Summer time in Northern New Jersey Suburbia. Checked numerous bug data bases of new jersey insects and came up empty handed. Thanks!
Signature: Gene Jefferson

Dead Brown Prionids
Dead Brown Prionids

Dear Gene,
These are Brown Prionids,
Orthosoma brunneum, and according to BugGuide:  “Breeds in poles, roots(?) in contact with wet ground” so they may be emerging from dead stumps you have in the vicinity.  They are also attracted to lights.  We are tagging this posting as Unnecessary Carnage as these two Brown Prionids do not look like they died of natural causes.

Letter 40 – Brown Prionid

Subject: BIG ONE
Location: Northern NJ
July 26, 2016 8:14 pm
Please tell me what this is! I have found 2 so far in my kitchen… July in NJ. They don’t seem to be doing anything wrong but they are so big! I would like to know if they are dangerous in any way. Thank you so much!
Signature: TB

Brown Prionid
Brown Prionid

Dear TB,
Though we always get reports of Brown Prionids each summer, this year there seems to be more than the usual number of sightings.  We suspect they are being attracted to your kitchen because of lights at night.

Letter 41 – Probably Brown Prionid

Subject: I’d large flying beetle-like insect which could be a hornet
Location: Tennessee
June 7, 2017 10:12 am
Flying at night. Loud. Black until opens wings, revealing a solid orange torso. Is this a hornet? Twice larger and thinner than any hornet I’ve seen.
Signature: Connie

Brown Prionid

Dear Connie,
This is NOT a hornet.  It is a Longhorned Borer Beetle in the family Cerambycidae, and though your image lacks critical sharpness, it appears to be a Brown Prionid.  More images are available on BugGuide.

You are amazing. Thanks so much for the info.

Letter 42 – Brown Prionid

Subject: what insect is this?
Location: westmoreland county Pennsylvania
July 6, 2017 1:28 pm
Curious as to what insect this is
Signature: Don Kirkland

Brown Prionid

Dear Don,
This is a Brown Prionid, a common summer identification request for our site.

Letter 43 – Brown Prionid

Subject: Bug
Location: Gays mills wis
July 13, 2017 11:14 am
Wondering what this is? Found outside on a rock near our pool
Signature: Brenda

Brown Prionid

Dear Brenda,
Comparing your image to this Bugguide image, this looks like a Brown Prionid to us.  According to BugGuide:  “Light brown, sides of elytra parallel. 11-segmented antennae, rounded, never flattened.”  Based on BugGuide data, Wisconsin is about the westernmost range of the Brown Prionid in the northern portions of North America.

Letter 44 – Brown Prionid

Subject: Large beetle in Pa!
Location: Northeastern Pennsylvania
July 15, 2017 7:23 pm
Hello!! I have never seen this bug in Pennsylvania before! It was a humid summer evening, and I noticed it on my outside screen. Nearly 2″ long it’s body alone, it made a squeaky kind of noise when it walked away from us on the ground. Took this picture as it was on the ground. What is this bug??
Signature: Debbie

Brown Prionid

Dear Debbie,
This impressive beetle is a Brown Prionid.  The squeaking you heard is called stridulation.  The beetle makes the sound by rubbing parts of its body together.

Letter 45 – Brown Prionid

Subject: Blister Beetle?
Location: Poughkeepsie, NY
July 25, 2017 5:48 am
Is the beetle in the attachment some sort of blister beetle? What is it?
Signature: Dave Jemiolo

Brown Prionid

Dear Dave,
This is not a Blister Beetle, and we do not believe any Blister Beetles attain this size.  This is a Brown Prionid, one of the Root Borers in the subfamily Prioninae.  According to BugGuide:  “Breeds in poles, roots(?) in contact with wet ground.”

Letter 46 – Brown Prionid

Subject:  this guy whacked me in the head
Geographic location of the bug:  Maine usa
Date: 07/17/2018
Time: 03:31 AM EDT
Your letter to the bugman:  Just curious I see this type of bug often.. took me a while to get the courage to put him back outside
How you want your letter signed:  brooke

Brown Prionid

Dear Brooke,
This impressive Longicorn is a Brown Prionid.  According to BugGuide:  “Adults come to bait, so presumably take some rotting fruit, sap?”

Letter 47 – Brown Prionid

Subject:  Large beetle
Geographic location of the bug:  Cape Cod, MA
Date: 07/27/2018
Time: 09:20 AM EDT
Your letter to the bugman:  I found this guy on my car this morning. I thought it was a June bug at first, but now I’m not so sure.
How you want your letter signed:  Donna

Brown Prionid

Dear Donna,
We just finished posting another image of a Brown Prionid.

Letter 48 – Brown Prionid

Subject:  What’s that bug?
Geographic location of the bug:  Avon, NY
Date: 08/10/2019
Time: 01:43 PM EDT
Your letter to the bugman:  Found it at night on our patio. About 2.5 inches long. Wings covered with brown somewhat  translucent hard shells. Moving vigorously around,  non aggressive. We moved it carefully to nearby meadow. What is this bug? Many thanks to whomever can give us a clue.
How you want your letter signed:  Nature lover.

Brown Prionid

Dear Nature Lover,
Orthosoma brunneum which is pictured on BugGuide is commonly called a Brown Prionid.

Letter 49 – Prionid from South Africa

Subject: Brown SA beetle
Location: Waterberg mountains, South Africa
November 26, 2015 5:54 am
The images of this brown beetle was taken in the Mabalingwe game reserve in the Waterberg mountains two hours north of Johannesburg, South Africa.
It may not look pretty but it does seem to have unusually serrated antennae. I wondered what it is?
Signature: Dave Smith


Dear Dave,
Your Longhorned Borer Beetle from the family Cerambycidae is a Prionid in the subfamily Prioninae, but we cannot provide a species name at this time.  There are many species pictured on iSpot.

Letter 50 – Prionid from Tanzania

Subject: Identification Request
Location: East Africa
January 19, 2017 7:28 pm
Hi there,
Here are a few interesting ‘bugs’ I photographed while living in Tanzania between 2008 and 2011. Hoping you can help me (finally) identify exactly what they are 🙂
Many thanks
IMG 8969 in Longido, Northern Tanzania (found dead)


Dear Tom,
This is one of the Longicorns from the family Cerambycidae, and it is one of the Root Borers in the subfamily Prioninae.  Based on this FlickR posting, it might be in the genus
Tithoes, however it does not resemble others from that genus on our site. 

Based on The Old World Cerambycidae Search, it appears to be Anthracocentrus beringei, but searching that name does not provide any additional information.  While we cannot with certainty provide you with a species, we are nonetheless confident it is a member of the subfamily Prioninae.   

Letter 51 – Prionid from Thailand

Subject:  I.D. of a Very Irritated Bug
Geographic location of the bug:  Thailand
Date: 09/15/2017
Time: 02:45 AM EDT
Greetings! If you could I.D. the attached bug, I would deeply appreciate it, as these manaical carnivores are rampaging throughout my house! I stuffed one in a jar, and it ate an entire snack bag of sweet pork jerky. I’m afraid I’m next on the menu. Thank you in advance for your efforts.
How you want your letter signed:  Suzanne Jamsrisai


Dear Suzanne,
This is a Prionid in the subfamily Prioninae.  It resembles 
Dorysthenes (Paraphrus) granulosus which we found on the World Wide Cerambycoidea site.  They are not maniacal carnivores, though the mandibles of large individuals might deliver a painful bite.

Letter 52 – Prionid Grub

Subject: Big Ol’ Larva – Carpenterworm?
Location: Raymond, California (Sierra foothills)
October 29, 2012 4:03 pm
We were splitting wood this weekend, and found this large larva inside one of the interior live oak rounds. We believe it to be a carpenterworm larva – can you confirm?

As you can imagine, it was not happy to have been revealed to the world, so our size comparison with the measuring tape isn’t quite in alignment.
Love your website!
Thanks so much
Signature: Megan Ralph

Prionid Grub

Hi Megan,
This is the grub of one of the Longhorned Borer Beetles, most likely a Prionid, and possibly the California Prionus.  See this image from BugGuide for comparison.
  According to BugGuide

“Larva feed primarily on living deciduous trees (oaks, madrone, cottonwood) and are also recorded from roots of vines, grasses, and decomposing hardwoods and conifers. Will also attack fruit trees growing on light, well-drained soils (e.g. apple, cherry, peach)”

Letter 53 – Prionid Larva

Subject:  Grub
Geographic location of the bug:  San Diego coastal 15″ below ground
Date: 01/20/2018
Time: 08:00 PM EDT
Your letter to the bugman:  I’ve never encountered a grub so large before and would like to know what kind of beetle this will become.
How you want your letter signed:  Matt Lee

Prionid Larva

Dear Matt,
This appears to be one of the Root Borers in the subfamily Prioninae.  Was there a tree or shrub nearby, or perhaps the trunk of something that had died?  While we are reluctant to provide a definitive species identification, it might be the larva of a California Root Borer like this image posted to BugGuide

According to BugGuide:  “Larvae: Up to 80mm long” and “Larva feed primarily on living deciduous trees (oaks, madrone, cottonwood) and are also recorded from roots of vines, grasses, and decomposing hardwoods and conifers. Will also attack fruit trees growing on light, well-drained soils (e.g. apple, cherry, peach).” 

If that is a correct identification, here is an image of an adult male California Root Borer, though your larva might belong to a different, though similarly large Prionid with long antennae. 

Prionid Larva

Letter 54 – Prionid Root Borer

SC beetle
I live on Hilton Head Island, South Carolina. I just saw this bug out on my back porch. I cannot find anything on the internet about it. I have never seen it before. It is about 2 inches long not including the antenna. Can you please tell me what it is? Thank you!
Sarah Hurst

Hi Sarah,
Your really big beetle is one of the Prionid Root Borers. We suspect it is Prionus imbricornis, the Tile Horned Prionus, but we would like Eric Eaton to confirm that identification.

Letter 55 – Prionid from Thailand, Probably Dorysthenes (Paraphrus) granulosus

Subject: Thai longicorn
Location: North of the Gulf of Thailand
April 9, 2017 8:40 pm
Hi, I found this longicorn at night at the start of the hot season (March) in central Thailand, right before two weeks of heavy rain showers.
It was about 8cm in length and I was able to pick it up, it did not hiss or squirm but may possibly have been dazed by a light.

The area where I found it is a small open grassy area, at the side of a reservoir and wetland, surrounded by protected tropical forest, not far from Chonburi on the coast of the Gulf of Thailand.

A week before finding this specimen, I saw the same species mating on a wall, and another drowned in a small puddle of water. Since March I have not seen any so possibly they were active to mate?
It would be awesome if I could get an ID!
Signature: Laura


Dear Laura,
Your Longicorn is a Prionid in the subfamily Prioninae.  Prioninae of the World has a page devoted to species found in Thailand, but not all species are pictured. 

Of the ones pictured on Prioninae of the World, in our opinion, the one that most resembles your individual is Spinimegopis lividipennis because both have several prominent spines on the thorax.  The species is also pictured on Cerambycoidea Forum.

Update:  April 29, 2017
Thanks to a comment from Tina, we agree that
Dorysthenes (Paraphrus) granulosus which is pictured on FlickR and on Coleoptera Atlas appears to me a very good possibility for a species identification.

Letter 56 – Sudanese Prionid Borer

Serious mandibles
hello bugman.
I sent you some photos the other day but you must be busy cause I havent seen them. They were mostly just pretty pics. I have a question about this critter. He is about 3-4 inches long and has these great big jaws.

Quite placid when he is still but if you touch his back, he spins around ready to attack. Is like a off brown with light brown mottled color markings. Quite agressive.

We are in the desert in Sudan and have plenty blister beetles, and awesome moths, one I ID from your site being the white lined sphinx. Thank you! Thanks for a very interesting site!
Marc B. Potgieter
Khor Abeche
Southern Darfur

Hi Marc,
Our mail volume is so heavy right now, we could not answer every letter if we spent 24 hours a day on the site. We choose letters at random. This is some species of Prionid Borer. It resembles the North American Derobrachus species.

The heavy mandibles are necessary as the large grubs are wood borers, often in roots. The adult needs to chew its way to the surface through the wood after it emerges from the pupa.

Letter 57 – Unidentified Prionid from Washington

Subject:  Weird bug found at work
Geographic location of the bug:  Grays harbor washington
Date: 08/11/2021
Time: 06:14 PM EDT
Your letter to the bugman:  Found this bug while I was at work and it’s massive, was probably 2 1/2 almost 3 inches. kinda think it’s a June bug but it doesn’t got the stripes
How you want your letter signed :  What is it?

Unidentified Prionid

We are only able to provide you with a partial identification on your discovery.  This is a Longhorned Borer Beetle in the family Cerambycidae, and it is a member of the subfamily Prioninae, the Root Borers.  Unfortunately we are unable to provide you with a species name. 

Though you submitted three images, one was a red rectangle and one a black rectangle with no insects visible.  The image we posted has many identifying features hidden in the grass. 

The gray coloration and lack of thoracic spines are distinctive, but it doesn’t look like any of the species on BugGuide.  Is Grays Harbor a town that gets international ships?  Perhaps one of our readers with more experience will be able to provide a species identification. 

Sorry it wouldn’t let me put anymore pictures on because there wasn’t enough space for 2 pictures but I do have a video and we just got a storage container from China at my work like 4 months ago.

Letter 58 – Who left the Head of a Prionid Beetle on Kerri’s Deck???

Should this even be in New Hampshire?!
Location: New hampshire
June 30, 2011 6:29 pm
This little creature made his way onto my deck last night, as to where he came from or his name that unforuntaly wasnt attached to him.. Im questioning if this should even be in new hampshire, i have never see anything like it!
Signature: Kerri

Head of a Prionid Beetle

Dear Kerri,
We feel like we have been involved in a Sherlock Holmes novel or a CSI episode.  This is the head of a Prionid Beetle, and there are numerous species that might be encountered in New Hampshire.  Our most likely subject is a male Broad Necked Root Borer,
Prionus laticollis, which is pictured in our archives and on BugGuide where it is indicated that:  “Antennae have 12-13 segments.” 

The head you found appears to have 12 segments on the antennae.  The big question is how did that head get on your deck.  Birds will sometimes eat fatty insects, and the body of a Prionid Borer is full of fat, and the head hasn’t much nutritional value, not to mention it is harder and less palatable.   BugGuide also indicates:  “Males are attracted to lights.” 

This is a male as females have much less developed antennae.  If this Prionid was attracted to a light and your house cat encountered it, perhaps the cat ate the body of the insect and left you the head as a trophy.  The predator will have to remain a mystery.


  • 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.

93 thoughts on “Brown Prionid: All You Need to Know About This Fascinating Beetle”

  1. we found a orthosoma burneum in our pool today. He is now resting in my 7 year old son’s bug trap overnight. He seems to burrow in the soil. Will he be okay overnight with roots and soil?
    Buggy brewers, west hartford, CT

  2. That’s definitely quite strange, and fun to try to figure out, but I do feel sad for the poor little thing. If it was windy and the windows were open, it could have been blown in from somewhere. Sometimes birds will just eat the bodies of insects, and regurgitate the rest of it up because it gets caught in their throat.

  3. I found one of these here in Abilene, TX! it’s huge! My miniature pincher was barking like crazy at something in the grass. Upon further investigation it was the biggest bug I’ve ever seen! It is about 3″ long (the size of my Dodge truck key).

  4. I -THINK- I saw another one of these guys about 25 miles south of Boston, MA. Only saw him from beneath, though, because frankly after he thumped against my window I locked up the house tight, shut the shades, and cried for a bit.

  5. I just found one of these on my screen door here in Orange, Ct. 7-19 I have not seen one of these before. Are they known to be in Ct? It’s beautiful and very large!!

    • Connecticut is within the range of the Brown Prionid, but interestingly, a sighting map based on BugGuide submissions does not include any Connecticut sightings. You should submit an image to BugGuide to color in the map. There might be other factors in the dearth of sightings in Connecticut, but we suspect it is because of a lack of submissions rather than an environmental factor, however, ranges of native species often contain gaps in sightings.

  6. I just caught my 10 month old schnauzer pup “playing” with one of these in the backyard. I’ve never, never seen one before and I can’t figure out where the little darlin’ found it. Schnauzers are great sniffers, so she probably chased it down from under some shrubs Thank you for your website! I live in Suffolk County Long Island.

  7. Just found one of these crawling up our front porch wall in Reading, Pa. Got a great picture of it. How do I send it to you or post it? I’ve seen similar sawyer type beetles but never one of these.

  8. Ah! That is definitely him. I was looking at Hardwood Root borers and Pine Sawyers, which were all similar, but none looked 100% like the one I’d found. This one certainly is!

    Not to worry about the state of the prionid, I released him into the remains of a fallen tree an hour or so after sending this in and taking measurements. He’s safe and sound. It’s good to know he’s a native species, so I’m glad I saved him from my mother’s angry boot that night.

    Thank you! 🙂

  9. Ah! That is definitely him. I was looking at Hardwood Root borers and Pine Sawyers, which were all similar, but none looked 100% like the one I’d found. This one certainly is!

    Not to worry about the state of the prionid, I released him into the remains of a fallen tree an hour or so after sending this in and taking measurements. He’s safe and sound. It’s good to know he’s a native species, so I’m glad I saved him from my mother’s angry boot that night.

    Thank you! 🙂

  10. Wow! I just had one on my screen door as well! Freaked me out, thought it was a female rhino beetle. The dog was put-off by it sitting there. It must be their time of year. I, too, have lived in my area (Franklin, MA) for about 3 decades and had not recalled seeing one before. I was not afraid but I was taken aback by it. It is pretty awesome.

  11. Found one running across my family room floor. I also thought it was a roach,,,which I had never had in our home. We do have about 80 trees/shrubs on our property along with some rotting stumps. Our home is about 120 yrs ofls with clapboard siding. could these become a problem? We just had our home painted. the painting crew said that our property has the most unusual insects that they’ve ever seen. Now I’m worried.

    • Brown Prionids will not damage your home. If you are paranoid about insects, perhaps that is not the ideal location for you. We would be more than happy to attempt to identify any insects that concern you if you email images using our Ask What’s That Bug? form. What is ofls? Some cryptic form of “awfuls” perhaps?

  12. Just had one of these scare us while sitting on our patio. Large Brown big antenna and loud. We are in Thousand Oaks, CA.

    • That is a very good possibility, though they generally appear later in the year. This was a warm winter in California, so that might have some influence on an earlier than typical appearance.

  13. Never seen one in my 60 yrs on Earth. Nobody I showed it to had seen one either–new to Pennsylvania? Was found dead on sidewalk outside office bldg doors. Had to look it up to find out what the h the thing is. Almost 2″ long makes it a scary looking creature.

  14. Found a swarm of bee-like insects buzzing around cellar window. Sound like bees, shaped like bees, about size of a honey bee, but appeared black with touches of white. Looked for it in my insect book but unable to find. Any ideas?

  15. Is this bug also in Canada? It’s where I live and one bit me on the back while I was on my computer… It looks really close to the picture but I don’t know if they’re in Canada and if it’s the right bug. Help?

  16. I’ve found three of these in my bedroom in the past week. Although I assumed they weren’t considered harmful, one was huge (about 1.5-2 inches) and the others were a little less than an inch so I’m worried that the larger one laid eggs somewhere. Are they invasive? Any tips on making sure there are no more in my room?

  17. One of these was found in yakima washington in a friends swimming pool. It looks like theyre mostly found in the east coast. Just wondering if these guys have changed migratory paths

  18. Thanks for the explanation, I understand the difference now. At least I got the brown part right. He (?) was very handsome.

  19. I just found a brown Prionid on my screen door here in Grand Rapids MI. it was as big as my thumb – almost honey color.

  20. Hey, I live in New haven, CT and have found 2 huge ones (about an inch) of these and 2-3 smaller ones about 1/2 an inch in my house over the last week or so, our house was built in 1900 as well and is down by a river… do they click and try to bounce away when you try to get them or is that just something they’re doing for me? scares the hell out of me lol

  21. Sad that I just killed one while freaking out mistaking it for a roach ( palmetto bug) after just returning from Florida.. I’m here in Massachusetts , Cape Cod and I may have seen one before but not many ..

  22. Just found one in my dogs feeding bowl of all places. Got good picture, very impressive, large beauty. About 2″ and bit through a twig I put by it’s mandibles.

  23. Dear sir

    I am looking for long horn beetles in puerto Rico. And want to buy dried insects there.
    For more information, contack me by my e-mail. Thank you very much

  24. Dear sir

    I am looking for long horn beetles in puerto Rico. And want to buy dried insects there.
    For more information, contack me by my e-mail. Thank you very much

  25. Just saw one of these on an outside window. I absolutely cannot stand bugs and this thing is the stuff of nightmares for me! It was at least 2″ long. We live in a rural town in Tennessee, in a neighborhood. I have never seen one of these in my life. Do they fly? If it’s hot outside, could it come in the house or will it stay outside? It eventually got off the screen somehow and I next saw it crawling on the patio. I will probably have a heart attack if one of these come in my house. If I saw ONE, does that mean there are others? If so, where would they be found?

    • They are attracted to lights, but they are not interested in living indoors. If one is found in the house, it was an accidental intrusion.

  26. I just found one on the side of my house in Long Island, New York. I’ve read they live in telephone poles and such. I recently found large holes in the pole for my mailbox, which is like a short telephone pole. There were 5 holes, each perfectly round and 3/4-1″ in diameter. Could this be from these beetles or something else, like a carpenter bee?

  27. I live in NS Canada, and found two of these in a bucket of water the other morning. What terrifying looking bugs! Are they out during certain months in the summer, kind of like June Bugs?

  28. I just found a large one of these guys on my front porch in Burlington Vermont. When I touched him he began making “hissing” noises and scurrying away.

  29. Just had one fly up to our porch!! (Southwestern Wisconsin) I’ve never seen one before. SO BIG!!
    I caught it in a glass and let it go about 3 blocks away 🙂

  30. Just had one fly up to our porch!! (Southwestern Wisconsin) I’ve never seen one before. SO BIG!!
    I caught it in a glass and let it go about 3 blocks away 🙂

  31. my mother has encountered this thing crawling in her shirt last night. what do we do. do we kill it. and are there possibly more? i would post a pic of it but i cant.

  32. One of these flew into the house earlier in Mount Airy, NC. Finally got him and put him out. I’ll be danged if it wasn’t right back in the window in less than 3 minutes. Scared the life out of me. Second time I got it the sucker bit me! Sadly, it’s dead. I’d never seen one and didn’t want to risk it biting one of the children. I believe I know why I saw it though. It’s a “new” old house, unkept yard and garden. We overhauled today and that meant moving rotten wood in the yard, cutting foot and a half grass, etc. Lots of weird bugs running around now that we weren’t seeing before.

  33. My son and I saw this thing moving across my living room rug at 11;00 at night. We freaked out and caught it. Over 2 inches long. It is a brown prionid beetle. I’m concerned about it leaving others in the house. I have alot of old tree around my house and a rotting stump that I have been picking at. Do I kill it or let the birds eat it. Hopefully no young ones in my house again. I’m vacuuming often again.

  34. Hi I just found one in Bucks County Pennsylvania hiding under some fiber pots. When it was exposed to the sun it acted like a vampire and scurried to find a hiding place. When I tried to help it to a better spot it hissed at me. It is ominous and I almost wanted to eliminate it due to its cockroach like appearance but I talked myself out of it after inspecting the tail end and antenna. I have a very important question though, is this a good or bad bug for the garden? what does it eat? I have pictures if you are interested.

    • The hissing sound you heard is an action known as stridulation and is produced when the insect rubs parts of its body together. In our opinion, the Brown Prionid is a benign insect, and according to BugGuide: “Breeds in poles, roots(?) in contact with wet ground” indicating the larvae feed on rotting wood.

  35. I live in Staten Island, NYC. I live near old trees and wetlands — I see these a few times a year in the summer. They get in my house every couple of years — but last night I was awoke by one CRAWLING ON MY CHEEK IN BED IN THE DARK. I jumped up and turned the lights on and saw it crawling in my WHITE sheets — I was horrified — but I stayed calm because I knew I had to catch him — which I finally did. He’s currently in my bedroom in a glass jar. I’ll post photos if anyone is interested.

  36. Was just awoken by the very same Brown Prionid and am now wide awake. Freaked out and stepped on it and many small white eggs were seen; about the size of a sesame seed but rice looking. Allentown PA here. Used the app Picture Insect to identify it. So much for tonight’s sleep!

  37. Awoke at 530 am to this guy and when I got close he chirped and flew off. I have a child here so I spent 2 hours looking for him to no avail. I fell back asleep and bam just woke at 830 to him flying around my room. Finally found what he was in here thanks. Mansfield, Ohio it’s been in the 90’s here.

    Why is there barely any info on them out there??

    • According to American Insects: “Orthosoma brunneum is most often noticed when it blunders into the human world, attracted to houses by electric lights.” Now that you have a scientific name, you should be able to locate additional information.

  38. Awoke at 530 am to this guy and when I got close he chirped and flew off. I have a child here so I spent 2 hours looking for him to no avail. I fell back asleep and bam just woke at 830 to him flying around my room. Finally found what he was in here thanks. Mansfield, Ohio it’s been in the 90’s here.

    Why is there barely any info on them out there??

  39. My brother and i were casually sitting watching Tv when a bug fell from what we thought was the ceiling. We immediately killed it and found small white seed looking things(looked like sesame seeds). We for sure thought it was a cockroach, but after further research we found out that it was a Brown Prionid Beetle. Any idea what the sesame seed looking things were? Are there any more of these beetles in my house? Should we be worried

  40. Worker found a brown prionid crawling in his workspace, a room in the center of a large warehouse. Can’t figure out how it got in. Caught it in a cup and is returning it to some wilderness next to the building. Lititz, PA.

  41. Just found one on my screen door and it scared the crap out of me! My husband told me it was a cockroach so I did my research – definitely a brown prionid beetle. I’m in Southern Wisconsin and this is the first I’ve seen one – and hopefully the last! Don’t worry – he looked peaceful so I let him be!

  42. There are here in Idaho too. Biggest beetle I know of around here.

    I just got done picking one up, but buy the shell, they look like they have some fierce mandibles!

  43. There are here in Idaho too. Biggest beetle I know of around here.

    I just got done picking one up, but buy the shell, they look like they have some fierce mandibles!

  44. Thank you.

    The beetle I saw last night looked just like the one in the photo above, and was 2in or more long not including the antennae.

  45. Found a dead but big dark Brown Prionid floating in a bucket of rain water earlier this week. Never saw one like this here before. – Lebanon County PA

  46. This guy scared the crap out of me when I caught him in a plastic cup that had a bit of water in the bottom, he started squeaking and I almost had a heart attack. Didnt know the little guy had it in him. Thought he was a cockroach at first too, thank the heavens hes not. I guesz its time to release him from beetle jail lol

  47. I had one of these fly into my bedroom window at night. It made like a squeaky noise and it was about an inch long. I’m from Hendersonville, NC.

  48. My daughter ready for bed on a hot muggy night on her phone was visited by this huge almost 2 inch beetle. She comes screaming out of her room. She is not a bug person. After this happened 3 times i was finally able to find and catch the huge Brown Prionid. We took many pictures and let it go the next day in the woods with lots of dead Scotch Pines for her to lay eggs. Harleysville,PA.

  49. Saw one of these today here in NJ. Impressive critter, more shiny bronze colored than dull brown. Easily 1.75″ long. Had to look him up!

  50. We live just outside of Philadelphia. Sitting in my office doing some work and my cat is going crazy near the desk shelves. I finally look and here’s one of these beetles! Now that I can identify it. Buzzing around. Captured it in a napkin and let it go outside. How did it even get in the house? Would it have been harmful to me or my cat?

  51. i have a tarp on the underside of my top deck for rain protection. while i was out feeding the feral cats i saw this giant brown bug on it but it was dark out..first thing when i got a flashlight and my glasses for better view i thought it was a palmetto bug since living in fla many years ago you never forget those things lol…anyway the face/head area wasnt the same and the antenna looked different but i just couldnt get a close look because i was afraid it would drop on me lol…thought id do a search of beetles in ct and this one came up right away and i believe it is what it is…i noted the head area was not the same as a palmetto before i came in to look online and when i saw a photo of this one i knew it was it…im in waterbury ct..and i also just learned that palmettos are not beetles..and why is it that i feel better knowing this is not a palmetto bug and just a giant beetle add a photo but i also have raccoon babies hanging around and when they hear the screen door they come running up looking for cat food. 🙂 thanks for posting everyone..its very helpful for someone like me who likes to research things i dont know 🙂

  52. I found one in my house last night (Stockbridge VT). It was laying on its back, kicking its legs trying to get back up. My first impressions is that it was a huge cockroach. Until I got up close and witnessed those scary/nasty looking pinchers as a mouth. I assume he was attracted to the light and squeezed into my house through the sides of a window unit air-conditioner. My wife would have had a heart attack if she found it. Will be sealing those open areas asap!

  53. These beetles seem to love July. I live in northern Indiana and I found a 2″brown prionid on the outside of the laundry room window tonight. We had some rain today and the night has been humid. The laundry room light was on so it was probably drawn to it. I’m glad it was on the outside of the window. They give me the creeps because they look so similar to roaches. I actually thought the one I saw was a roach at first.

  54. 8 years later from the 2 previous posts… I’m in Indiana. Never seen one in my 58 years! Saw one yesterday and appreciate this info. That bug freaked me out!

  55. Visited by one in our house on a hot and humid night. We have central AC but had a lot of company and doors open all day. My husband mentioned that he thought he saw something flying in the living room earlier in the evening . Huge bigger! Phoenixville, Pennsylvania


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