Hardwood Stump Borer: All You Need to Know Explained Simply

Hardwood stump borers are a category of insects that infest and cause damage to hardwood trees. They are commonly found in trees that are weak, diseased, drought-stricken, or recently dead. These pests may belong to different insect groups such as beetles, moths, and a single wasp species. Knowing more about them can help in managing their potential harm to our forests and landscapes.

One example of a hardwood borer is the cottonwood borer, which develops in tree roots and can wreak havoc on young trees. Other notable species include the clearwing borers, which are actually larvae of clearwing moths that have a striking resemblance to wasps. These borers are known to infest various trees such as peach, dogwood, lilac, and ash.

Identifying the signs of hardwood borer infestation is essential for timely intervention and treatment. Some common indications include holes in the bark and reddish frass (excreted wood particles produced by the borers) in bark crevices or around the base of the tree. By recognizing theseblem signs, effective control measures can be implemented to limit the damage caused by these pests.

Hardwood Stump Borer Basics

Insect Description

The Hardwood Stump Borer is a type of longhorn beetle known for its wood-boring larvae. This beetle is usually found infesting trees such as oak. Adult beetles vary in size, typically ranging from 5/8 to 1 1/4 inches in length. One distinctive feature of these beetles is their long, segmented antennae, which are located near their black or blackish-brown bodies.

Key features of Hardwood Stump Borer:

  • Belongs to the longhorn beetle family
  • Infests hardwood trees like oak
  • Adult size ranges from 5/8 to 1 1/4 inches
  • Long, segmented antennae

Scientific Classification

The Hardwood Stump Borer, scientifically known as Mallodon dasystomus, falls under the Cerambycidae family. This species is commonly found in Florida where it targets hardwood trees. Both males and females share similar physical characteristics, making them difficult to distinguish.

Comparison of Hardwood Stump Borer and other beetles:

Beetle Type Size Range Antennae Common Habitat
Hardwood Stump Borer 5/8 – 1 1/4 in. Long, segmented Florida, oak trees
Old House Borer 5/8 – 1 in. Short Homes, structural timbers
Carpinterworm 1 – 2 in. Long Soft and hardwood trees

Remember to be cautious when dealing with wood-boring beetles as they can cause significant damage to the hardwood trees they infest.

Life Cycle and Habitat

Eggs and Larval Stage

The Hardwood Stump Borer (Mallodon dasystomus), a type of longhorned beetle, starts its life as an egg laid on hardwood trees like willow, maple, and elm1. After hatching, the grub (or larva) bores into the tree, feeding on the wood and bark. The larval stage can last for several years before maturing.

Some key characteristics of the larval stage include:

  • Mandibles for chewing through wood
  • Ant-like appearance
  • Feeding on hardwood trees

Adult Stage

Once the grub reaches maturity, it emerges from the tree as an adult hardwood stump borer beetle. These beetles have the following features:

  • Length of 1-2 inches
  • Dark color with various patterns on the wings
  • Pincers for defense and biting
  • Nocturnal behavior
  • Ability to fly

The adult beetles lay eggs on trees, repeating the life cycle. They are mostly found in hardwood forest areas, among furniture, and wood structures2.

Geographical Distribution

Hardwood stump borers are primarily found in North America, more specifically covering Mexico and Arizona3. Their habitat consists of areas where hardwood trees are abundant, such as sandbars and forests. They thrive in environments with a high density of willow, maple, and elm trees. Insects of the family Cerambycidae, also known as longhorn beetles, belong to the kingdom Animalia, phylum Arthropoda, class Insecta, and order Coleoptera4.

Comparison Table: Hardwood Stump Borer vs. Ant

Feature Hardwood Stump Borer Ant
Classification Class Insecta Class Insecta
Order Coleoptera Hymenoptera
Length 1-2 inches 0.03-2 inches
Food Hardwood trees Largely omnivorous

Behavior and Diet

Feeding Habits

The Hardwood Stump Borer is a species of longhorned beetles that infest and feed on the heartwood of various tree species, primarily sycamore trees1. Their diet consists of:

  • Tree heartwood (mainly sycamore)
  • Wood grubs (larvae of other beetles) in some cases

The feeding habits of Hardwood Stump Borers make them economically damaging5 to the trees they infest, as they weaken the structure and compromise the tree’s health.

Mating and Reproduction

Mating for Hardwood Stump Borers typically occurs during the spring and summer months. Some key aspects of their mating and reproduction process include:

  • Mating season: Spring and summer
  • Egg laying: Females lay eggs in crevices of infested trees
  • Larval stage: Grubs feed on the heartwood and develop within the tree

Although these borers are not aggressive or dangerous to humans, their powerful jaws can cause painful bites if handled improperly. They are not known for being bloodsuckers or predators of other insects.

Hardwood Stump Borers are found in various regions across the USA, including North Carolina4. Infestations can be problematic for tree health but do not pose any immediate danger to humans.

Footnotes

  1. US Forest Service – Management Guide for Wood Borers 2

  2. University of Maryland Extension – Old House Borer

  3. Texas A&M University – Structure-Infesting Wood-Boring Beetles

  4. University of Kentucky – Old House Borer 2

  5. Old House Borer

Reader Emails

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

Letter 1 – Hardwood Stump Borer

 

HELP! Stenodontes dasystomus or Mallodon dasystomus? **with pics**
Bugman!
We are pretty sure this is a Stenodontes dasystomus or a Mallodon dasystomus. Is there a difference or did the latter replace the former. I’ve included 2 pictures, one that looks better than the one you already have listed. Let me know what you think! Thanks<
Vicki
North Texas

Hi Vicki,
Our first thought is that we are thrilled to be able to post your fine image of a Hardwood Stump Borer. BugGuide identifies the scientific name as Mallodon dasystomus and notes: “Mallodon or Stenodontes, which appears to be a synonym of Mallodon ” which indicates, at least for now, both names are correct.

Letter 2 – Hardwood Stump Borer

 

Subject: Big Beetle!
Location: Austin, Texas
July 18, 2013 6:31 am
Dear Bugman,
I’m from Austin, Texas and found this big beetle inside our apartment when we returned home from vacation. So I strategically picked it up and released it outside thinking I’d never see it again. Well, the next day there it was lurlurking around the entrance of the apartment. It’s been raining a couple of days so I figured maybe the rain washed it from its habitat. Can you tell me why type of beetle this is and is it harmful? Thanks in advance for your help.
Signature: Concerned Texan

Hardwood Stump Borer
Hardwood Stump Borer

Dear Concerned Texan,
“Harmful” and “harmless” are really such relative terms since even the most benign creatures can cause harm in certain situations.  This is a Hardwood Stump Borer,
Mallodon dasystomus, and it is not an aggressive species, but those mandibles which can chew through wood can most likely draw blood from anyone foolish enough to carelessly handle it.  According to BugGuide:  “Larvae bore in live heartwood of trees, incl. oak, elm, willow, pecan, maple, sycamore, etc.” and “take 3-4 years to mature. Can be economically damaging. Adults attracted to UV lights.”  Adult Hardwood Stump Borers will not damage your home nor its furnishings.  Larvae might be found in recently dead stumps.  We suspect this individual was attracted to lights and that is the reason you found it in your apartment.

Thanks Bugman! I tried to Google this beetle and was I was overloaded with web searches. I happen to stumble upon your website and I am pleased that I did!
Thanks again.
Concerned Texan

Letter 3 – Stout’s Hardwood Borer

 

Subject: beetle
Location: Hesperia, California
August 13, 2014 1:03 pm
what kinda of beetle is this.
i have alot of mealworm beatles
running wild from my own breeding.
could it have bred with a wild beetle
Signature: Brian

Stout's Hardwood Borer
Stout’s Hardwood Borer

Dear Brian,
Your image is not terribly clear, but this sure looks like a Stout’s Hardwood Borer,
Polycaon stoutii, to us.  We got that common name from Charles Hogue’s Insects of the Los Angeles Basin, but BugGuide refers to it as the Black Polycaon and has very little information about it.  Hogue on the other hand writes extensively about the Stout’s Hardwood Borer.  Hogue writes that they “appear in the fall (September) in unlikely places, such as in the hallways and rooms of new buildings, in warehouses, and in homes.  Their occurrence is explained by their breeding habits.  The larvae are wood borers that feed within various hardwoods such as oak, California Laurel, alder, maple, and eucalyptus — construction woods that are often used in building boxes, shipping crates, storage racks, and the slats used behind scoustic ceiling tiles;  the larvae will also infest finished wood products such as cupboards, cabinets, and furniture.  The adult Stout’s beetles may emerge from these products after the construction is completed and even after the product has been finished. … There is no evidence that the species reinfests lumber or manufactured wood products once the adults have emerged from them.”

Letter 4 – Stout's Hardwood Borer

 

September 8, 2010
Today while walking to the film lab between Union Station and Temple Street, Daniel noticed this Stout’s Hardwood Borer on a telephone pole.  He brought it our Mt Washington offices to photograph it because it is a very underrepresented species on our website.  We got that common name from Charles Hogue’s Insects of the Los Angeles Basin, but BugGuide refers to it as the Black Polycaon and has very little information about it.  Hogue on the other hand writes extensively about the Stout’s Hardwood Borer.  Hogue writes that they “appear in the fall (September) in unlikely places, such as in the hallways and rooms of new buildings, in warehouses, and in homes.  Their occurrence is explained by their breeding habits.  The larvae are wood borers that feed within various hardwoods such as oak, California Laurel, alder, maple, and eucalyptus — construction oods that are often used in building boxes, shipping crates, storage racks, and the slats used behind scoustic ceiling tiles;  the larvae will also infest finished wood products such as cupboards, cabinets, and furniture.  The adult Stout’s beetles may emerge from these products after the construction is completed and even after the product has been finished. … There is no evidence that the species reinfests lumber or manufactured wood products once the adults have emerged from them.”  Daniel can’t help but wonder though if the telephone pole in downtown Los Angeles was a likely breeding ground for the species.

This specimen is missing its left rear leg.

Letter 5 – Female Hardwood Stump Borer

 

bug!
I have never seen a bug quite this big before. I am also not quite sure what the "Stinger?" looking thing is. Any info?
thank you , Dolly Wade

Hi Dolly,
This is a female Hardwood Stump Borer in the genus Stenodontes. The stinger is her ovipositor. She uses it to deposit eggs under the bark so the larvae can burrow into the hardwood.

Letter 6 – Hardwood Stump Borer

 

Please Identify
Hello,
A week ago this bug in the attached picture showed up in my back yard in Allen, Texas just outside of Dallas. This bug’s very presence terrifies my wife and she needs to know what its call. It’s about two inches long not including antennae and legs. If you would be so kind as to identify my wife would appreciate it.
Thom

Hi Thom,
This is a Hardwood Stump Borer, Mallodon dasystomus. It is not an aggressive species and it will not try to attack your wife. She should, however, be aware that if she tries to pick up the Hardwood Stump Borer, it has very powerful jaws and can give a painful bite that might draw blood. Tell your wife that if she tries to handle the next Hardwood Stump Borer she encounters, she should use caution.

Letter 7 – Cylindrical Hardwood Borer

 

what the heck is this?
My parents live in New Jersey and found these in a maple tree they cut down…any help on this?

This is a Cylindrical Hardwood Borer, Neoclytus acuminatus. The larvae feed on many types of hardwood and are also found in unseasoned lumber. Adults are found on flowers and move very quickly.

Letter 8 – Hardwood Stump Borer

 

found three of these so far…
I’ve found three of these in as many days floundering about in my living room. The first one showed up Thursday, June 12 after a week or so of 95 degree days. Just wondering if my floor joists are going to cave in. Mount Pleasant, SC (next to Charleston)

This is a Hardwood Stump Borer, Mallodon dasystomus. We found a visual match on BugGuide. This species is attracted to lights, which could explain its presence in your home. If you have firewood in the house, the Hardwood Stump Borers might also be emerging from the wood.

Letter 9 – Hardwood Stump Borer

 

What is this bug?
Love your website. Can you help me identify this bug? We found it already dead and partially hanging out of one of many holes in a railroad tie approximately one inch in size. Thanks for your help,
Cheri Mosley

Hi Cheri,
Your photo is of the traumatized remains of the Hardwood Stump Borer, Stenodontes dasystomus. Your specimen is a male as evidenced by the robust mandibles. The larvae live in the heartwood of living trees, taking three or four years to mature.

Letter 10 – Hardwood Stump Borer

 

Pine Sawyer Longhorn beetle or neither?
My wife found this "little" friend of ours crawling around our bedroom in Virginia Beach and trapped it for me to see when I got home. I snapped a couple pictures and then let it go out back and took a few more that better show off the color. The first image I saw that was comparable looked like it could have been a Pine Sawyer, but now I’m thinking it’s some kind of Longhorn. Which is it?
Thanks,
Doyne

Hi Doyne,
Your two possibilities are not mutually exclusive. Longhorn Beetle is a general common name for the Family Cerambycidae. Pine Sawyer is a common name for several different genuses within that family. Your beetle is one of the subfamily Prioninae. In our opinion, it is one of two species. More likely the Hardwood Stump Borer, Mallodon dasystomus, but another possibility is the Live-oak Root Borer, Archodontes melanopus.

Letter 11 – Hardwood Stump Borer

 

What beetle is this?
December 30, 2009
I caught this huge beetle flying around outside my classroom window in Mesa, Arizona in the middle of April. On a warm sunny day.
My class thought it was a “flying spider”! What is it? any ideas? It’s not in any of my bug books. I enclosed two photos. Thanks in advanced for any help! 🙂
Lisa
Mesa, Arizona

Hardwood Stump Borer
Hardwood Stump Borer

Hi Lisa,
Your beetle is a Hardwood Stump Borer, Mallodon dasystomus.  You can find additional images and information on BugGuide.

Letter 12 – Hardwood Stump Borer

 

What kind of beetle is this?
May 18, 2010
I found this beetle on it’s back on the floor of my kitchen at about midnight. My first instinct was to “KILL THE BUG!!”, but then I thought that I should check out what kind of beetle it is to make sure my orange tree is safe. Thank you for your time. I want to apologize for the small amount of glare, didn’t want to let it out of the bag.
Chris
Orlando, Florida

Hardwood Stump Borer

Hi Chris,
This Longhorned Borer Beetle is a member of the Tribe Macrotomini, and though this particular view through the plastic bag is not ideal for identification, we are relatively confident that this is the Hardwood Stump Borer, Mallodon dasystomus.  According to BugGuide it has:  “Robust, gigantic jaws
” and “Larvae bore in live heartwood of trees, esp. oak, sycamore, take 3-4 years to mature. Can be economically damaging. Adults attracted to UV lights.”  We suspect it may have been attracted to the light in your kitchen.  It will not harm your orange trees.

Letter 13 – Hardwood Stump Borer

 

big beetle in my stump
Location: Miami, FL
May 3, 2011 7:00 pm
Hi there,
I’m a longtime fan, first time emailer!
I live in Miami, FL, and I have a big rotting stump in my yard (it was there when I bought the house; I don’t know what species it was). Last week my nephew noticed a pair of very large (~2” long) black beetles emerging from it. Since then, I’ve noticed that they emerge every day, right before dusk. I have found similar beetles on bugguide.net, but none with these exact feature. Can you help? Thanks! Note: in the photo, my beetle is covered in sawdust from a hard day’s work of stump-boring.
Signature: Jennifer P

Hardwood Stump Borer

Dear Jennifer,
Welcome to the ranks of the active contributors to our website.  We hope this is not your last submission.  This is one of the Prionid Root Borers in the subfamily Prioninae.  We believe it is the Hardwood Stump Borer,
Mallodon dasystomus, and here is the link to the Bugguide species information page.  Adult Prionids have very strong mandibles that are needed to gnaw their way out of the galleries they excavate in tree stumps and roots as larvae.  While they are not aggressive nor are they considered dangerous, their mandibles would most likely draw blood should they be carelessly handled.

Dear Daniel:
Thanks so much!  I love your website.  Thanks for providing such a wonderful service to the bug-curious people of the world.
Jennifer

Letter 14 – Hardwood Stump Borer

 

Large Ground Beetle???

Hardwood Stump Borer

Location: Union, MS
June 14, 2011 10:04 pm
A large beetle flew into my screened-in back porch, and I’m having trouble identifying it. It is 2” (50mm) long, and 5/8” across at the top of the wings. I have seen some photos that are similar, but not an exact match. Any idea of what this beetle is? I have a few more pictures if you need them…
Signature: Joey Graham

Hardwood Stump Borer

Hi Joey,
This positively magnificent beetle is one of the Prionid Longhorn Borers, and more specifically, it is
Mallodon dasystomus, the Hardwood Stump Borer.  Adults are attracted to lights according to BugGuide.

Hardwood Stump Borer

Letter 15 – Hardwood Stump Borer

 

Brown Beetle
Location: Central Florida
April 10, 2012 9:32 pm
I found this huge beetle on our front window. Do you know what kind it is?
Signature: Shari

Hardwood Stump Borer

Dear Shari,
This magnificent creature is
Mallodon dasystomus, commonly called the Hardwood Stump Borer.  According to BugGuide:  “Larvae bore in live heartwood of trees, esp. oak, sycamore, take 3-4 years to mature. Can be economically damaging. Adults attracted to UV lights.”  While this is not a venomous species, a nip from those “robust, gigantic jaws” would likely be quite painful and could possibly draw blood.

Letter 16 – Hardwood Stump Borer

 

Subject: Mallodon Dasystomus?
Location: Upper Texas Coast
May 22, 2017 3:47 pm
On Saturday night this not-quite-two-inch beetle came to our door. It seems to be Mallodon dasystomus, the hardwood stump borer, and displays the characteristic golden fur on the inside surface of its mandibles.
I live on the Upper Texas Coast near Houston.
Signature: Lachlan

Hardwood Stump Borer

Dear Lachlan,
We believe you are correct that this is a Hardwood Stump Borer.  According to BugGuide:  “Larvae bore in live heartwood of trees, incl. oak, elm, willow, pecan, maple, sycamore, etc” and “take 3-4 years to mature. Can be economically damaging. Adults come to lights.”  However, we would not rule out that it might be a Live Oak Root Borer,
Archodontes melanopus, which is also pictured on BugGuide.  We will attempt to get an exact species identification for you.

Letter 17 – Hardwood Stump Borer

 

Subject: Please identify this huge bug
Location: Austin Texas
July 3, 2017 4:40 pm
Hey man –
Hope you are well!
This is the third of these huge beetles I’ve found in the last few months. The first one was a couple of months ago, and it was dead. The next one was a couple of weeks ago and i put him outside after finding him in my house. Then this one I saw last night outside my front door.
What is this? It’s huge, maybe 2 inches long (I didn’t have a ruler and am a poor judge of size, so take that with a grain of salt). It showed up in late June in Austin Texas.
It kind of looks like another bug I found on your site, but I’m not sure.
Thanks man!
Signature: John

Hardwood Stump Borer

Dear John,
This Hardwood Stump Borer,
Mallodon dasystomus, which we identified on BugGuide, is an impressive creature.  According to BugGuide:  “Larvae bore in live heartwood of trees, incl. oak, elm, willow, pecan, maple, sycamore, etc.”

Letter 18 – Hardwood Stump Borer

 

Subject:  BBB – Big Black Beetle
Geographic location of the bug:  Upper part of South Carolina
Date: 06/28/2021
Time: 12:09 AM EDT
Your letter to the bugman:  Found this bug on my back porch at night under a light. Had some scary looking chompers. Can you identify?
How you want your letter signed:  Anthony Kozakiewicz

Hardwood Stump Borer

Dear Anthony,
We feel confident that this is a Hardwood Stump Borer,
Mallodon dasystomus, which is pictured on BugGuide.  According to Beetles of Eastern North America by Arthur V. Evans:  “Mandibles nearly horizontal” while of the similar looking Live Oak Root Borer, Archodontes melanoplus, the author writes:  “Mandibles nearly vertical.”

Hardwood Stump Borer

Letter 19 – Hardwood Stump Borer found in Toilet!!!

 

Subject: What is this?
Location: Houston, Texas
May 26, 2014 5:02 am
This was quite a surprise as I was getting ready for work at 3AM.
I found it in my toilet. It must’ve crawled out from the vent above it or something. It’s about 2″ long and has some large mandibles/jaws.
Signature: Ben

Hardwood Stump Borer
Hardwood Stump Borer

Hi Ben,
This is a Root Borer in the subfamily Prioninae, and we believe it is a Hardwood Stump Borer,
Mallodon dasystomus, based on images posted to BugGuide where it states:  “Adults attracted to UV lights.”  We suspect this individual was attracted to lights near your door and then got trapped inside where it succumbed to its premature drowning.  According to BugGuide:  “Larvae bore in live heartwood of trees, incl. oak, elm, willow, pecan, maple, sycamore, etc.”  The presence of any of those trees nearby would explain its appearance.  Generally, we get reports of Prionids later in the summer, but according to BugGuide’s data page, sightings of Hardwood Stump Borers in Texas have been reported from April through October.  We are happy you noticed this Hardwood Stump Borer prior to using the toilet, otherwise, you might have received quite a shock.

Hardwood Stump Borer
Hardwood Stump Borer


Letter 20 – Hardwood Stump Borer from Mexico: Callipogon barbatus

 

Myan Beetle
Found this guy just south of Cancun, Mexico
Doug

Hi Doug,
This is a Hardwood Stump Borer. We expect to hear from David Gracer that the large grubs are edible and were eaten by the Mayans. Those mandibles look like they can do some damage and we are curious why the Mexican tourism board does not picture this magnificent Beetle in their brochures. Eric Eaton wrote in with this information: “Daniel: The “hardwood stump borer” from Mexico is actually Callipogon barbatus. It is a male, as females do not have such enlarged jaws. I’ve never seen an image of a live one before! Very cool. Eric”

Letter 21 – Mating Cylindrical Hardwood Borers

 

Cylindrical hardwood borers mating
Dear Bugman,
Despite the crappy picture quality, my sister the biology teacher was able to identify these bugs for me. I watched them for much longer than I’m willing to admit. The mating ritual was pretty funny. Two or three of these guys were running back and forth, back and forth along an almost vertical segment of a mostly-dead tree. Each time one got to the end of the vertical segment, it would turn around and dart in the other direction. About every twentieth pass, two bugs would run into each other and mate. They’d finish (or he’d get tired of holding her down) and take off in opposite directions. Back and forth, back and forth…Then they’d run into each other again and the fun would resume. This went on long enough for me to go back to the house and fetch the camera. Unfortunately, my camera isn’t good enough to take top-notch close-up pictures.
Nancy

Hi Nancy,
What your photos lack in technical quality, you more than make up for with your colorful account of the mating ritual of the Cylindrical Hardwood Borer, Neoclytus acuminatus.

Letter 22 – Possibly Hardwood Stump Borer

 

Subject: Very large roach-like beetle?
Location: Santa Rosa Beach, Florida
August 26, 2013 6:02 pm
Hi! I am in the panhandle of Florida, right on the coast. Today I was very surprised to find what looked like the Mother of All Cockroaches outside of my office. The bug was about 3.5”-4” long and very wide- about 1”-1.25”. He had very thick legs and had wings. He looked very much like a cockroach except for his slightly curled, droopy antennae. I think he was injured (he was in the same spot most of the day) so I didn’t get to see how he moved. Also, sorry for not getting anything in the picture for scale – I was too terrified!
I hope you can help me. Thanks!
Signature: Natalie

Possibly Hardwood Stump Borer
Possibly Hardwood Stump Borer

Hi Natalie,
We wish you had a better view of the head and mandibles on this impressive beetle.  This is a Longhorned Borer Beetle in the subfamily Prioninae, but we cannot be certain of the species.  Based on the antennae and the thoracic region, it most closely resembles the Hardwood Stump Borer,
Mallodon dasystomus, which you can view on BugGuide.

Thank you for responding! Very interesting!

Letter 23 – Potential Hardwood Stump Borer and a Striped Caterpillar Aggregation from Mexico finally identified as Arsenura armida

 

beetle and caterpillar from Mexico
Hi there,
I know you are specialized in the bugs of North America but while browsing your great site I noticed you sometimes have exotics as well, so I thought I might give it a try. Since August last year we live in Quintana Roo, Southern Mexican Caribbean and just love the wide variety of animals especially the insects here. We always try to find out what we have seen, but there are some we couldn´t identify so far. Any ideas about this huge beetle or the big caterpillars that all gathered at this tree. The cute yellow and black one was quiet small. Thanks a lot!
Jacqueline

Hi Jacquiline,
Your beetle is a Cerambycid, one of the Longhorn Borers. It looks suspiciously like the Hardwood Stump Borer, Mallodon dasystomus, which is the only species of the genus found in North America. We could not locate any images online of Central American species, and perhaps one of our readers can provide an answer. Regarding the Striped Caterpillar Aggregation, we received another photo of this caterpillar in August 2006 and it is still unidentified.

Update: (06/30/2008) Arsenura armida Caterpillars
With our fourth submission of Caterpillar Aggregation images, we are convinced that this species is Arsenura armida, a Neotropical Silkmoth that ranges from tropical Mexico to Bolivia and Southeastern Brazil. We just located a website with valuable information written by James T. Costa , Department of Biology Western Carolina University, Cullowhee, NC.
Ed. Note:
July 8, 2009
Back in November 2007, Eric Eaton wrote in to identify another image of this beetle as Callipogon barbatus.  According to an online website, the species if found in Guatemala and Panama though our submissions hail from Mexico.

Letter 24 – Stout's Hardwood Borer

 

Eating my nightstand
Dear Bugman, I built these nightstands a year ago. Clean clear pine case w/ madrone top(old worm holes in top). I awoke up one morning to fine a dime size mound covering 7mm hole. Two days cat and mouse, and I caught this little guy. Two days later, another mound. Ergates spiculatus? We are very fond of our matching nightstands. Please advise if you will. Thank you,
A C Pitt.

Dear A C Pitt,
Way too small for Ergates. This is Stout’s Hardwood Borer, Polycaon stouti. Adults frequently apper in homes because the larvae bore in a great variety of hardwoods including oak, maple, alder, eucalyptus and laurel. The larvae infest the wood and construction of the product and finishing the wood does not deter them from continuing to feed. Then the adults emerge often from furniture, cupboards and cabinets. I guess the old wormholes should have been an indication that there was an infestation.

Letter 25 – Stout's Hardwood Borer

 

What is this beetle?
This beetle was flying noisily around our kitchen last night in Ventura, CA. We caught it and put it in a jar. It fell asleep around 11:00PM. It was still quiet this morning when I took the pictures. I left it outside on the jar lid, and after a while it climbed out and hid under the lid.
Thanks
Dennis Strauss

Ed. Note: Shortly after writing to us, Dennis wrote back that he located his beetle in Hogue’s Insects of the Los Angeles Basin. He identified it as Stout’s Hardwood Borer, Polycaon stouti. The larvae are wood borers found in oak, maple and eucalyptus among other trees. Adults often emerge from wood used in construction.Here is part of Dennis’ second letter:

I’m guessing it came from one of the eucalyptus trees behind our backyard wall. We don’t have any wood furniture less than 10 years old, and our house was built in 1991, so I don’t think it hitched a ride into the house inside anything manufactured.
Dennis Strauss

Letter 26 – Stout's Hardwood Borer

 

Subject: Bug to Human Detente
Location: Los Angeles, CA (Venice)
August 17, 2012 6:12 pm
hello experts. so clearly I know who I am, but the idiotic human who scooped me off his floor last night has nary a clue. after eyeballing me for what felt like ever (i have my pride) he placed me carefully in a glass with a bit of dirt, some blades of grass and a small drop of water (moron)… as if I am some common insect!! I tried to communicate with him but his telepathic abilities are far from advanced. I have included a few self-portraits along with his email in hopes that you can tell the misguided man who I am, a bit about me and where I should be released…. thank you in advance, Mystery.
Signature: Mystery, the Matte Black Wonder Bug

Stout’s Hardwood Borer

Dear Mystery, the Matte Black Wonder Bug,
Tell the “idiotic human” you are a Stout’s Hardwood Borer and (s)he may read about you in our archive.  You are only the second representative of your species on our website and the first example of a Stout’s Hardwood Borer was discovered by our staff on Temple Street downtown and brought back to the What’s That Bug? offices to be photographed.  Though the Stout’s Hardwood Borer,
Polycaon stoutii, is well represented on BugGuide, there is not much information except “Named after Dr. A.B. Stout, a friend of John LeConte who provided him with the first specimen.”

Letter 27 – Stout’s Hardwood Borer

 

Subject: Stout’s Hardwood Borer
Location: Central Hollywood
May 22, 2013 7:56 pm
This is an insect I understand is under represented on your site. I have seen tow of them in and around my apartment. I think it is kinda cute, but it’s jaws scare me a little. I put him outside by the big OLD tree. I hope he is happy there.
Signature: Jessica Brecker

Stout's Hardwood Borer
Stout’s Hardwood Borer

Dear Jessica,
We felt obligated to lighten and crop your image.  We are very impressed with your graphic composition.  You have good sense to be cautious about the mandibles of the Stout’s Hardwood Borer.  It chews its way out of dead wood including, we suspect, telephone poles when it ecloses into an adult.

Letter 28 – Stout's Hardwood Borers

 

Subject: Stout’s Hardwood Borer
Location: Redwood City, CA
September 28, 2012 6:23 pm
We seem to have had an ’infestation’ of sorts for the past month. I don’t know how they are entering the office, but we are on the 2nd floor and there are quite a few trees outside. These guys fly around, are up on the carpeted walls, or in boxes. They bite each other’s legs off if kept in the same container.
Signature: -D

Stout’s Hardwood Borer

Hi D,
Perhaps you have some new construction or new furniture at your office and wood that was infested with Stout’s Hardwood Borer larvae was used as a raw material.  Your observation that they bite each others’ legs off might explain why this Stout’s Hardwood Borer from our archive and this individual that our editorial staff photographed are also missing legs.  It is possible that males battle with one another for dominance.

Stout’s Hardwood Borers

Authors

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  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

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  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

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12 thoughts on “Hardwood Stump Borer: All You Need to Know Explained Simply”

  1. So glad to find this info. This morning I found what I think was one of these struggling in a parking lot here in El Salvador. We moved it to a tree near by. It was huge! I have never seen such an enormous insect/beetle. Minimum four inches. Wish I’d had my camera. The mandibles were much smaller than the ones in your photos. Also, the legs seemed longer, more spindly.

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  2. I found a whole nest of these swarming through some dead tree trunks in my backyard earlier this year…unfortunately found a couple roaming near the fireplace too after I’d brought some wood in for the fire.

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  3. I have a bug that resembles a hardwood stump borer with a few differences. One the antennae are smaller and the back has smaller lines but more of them . It is about the length of a penny.

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  4. Daniel and Lachlan , I believe that you have a wonderful specimen of Mallodon dasystomus ! Cheers ! Gene St. Denis Sierra Nevada Research

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  5. Big 2.5″ one of these lurking around my front stoop tonight in northwest Georgia. Have never seen such a mean looking bug…had to look it up. Thank you for helping us identify it.

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  6. Could you tell me what the adult stump borers eat? I’ve seen sites claim they are predatory, but that goes against the general wood boring beetle lore.

    Reply
    • According to BugGuide: “Larvae bore in live heartwood of trees, incl. oak, elm, willow, pecan, maple, sycamore, etc.” There is no information on the diet of the adult. It is possible they do not eat. They are definitely NOT predatory.

      Reply

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