Root borer beetles are a diverse group of insects that can cause significant damage to trees and shrubs. These beetles’ larvae bore into a plant’s roots, disrupting the flow of nutrients and water, ultimately weakening or killing the plant. Knowing how to identify and control these pests is crucial for maintaining healthy landscapes and gardens.

There are several types of root borer beetles, including clearwing borers, which are larvae of moths that resemble wasps, such as peach tree, lesser peach tree, dogwood, lilac, and ash tree borer borers. Another common borer found on shrubs is the rhododendron stem borer, an invasive pest primarily affecting Prunus plants, such as cherry laurels rhododendron stem borer. Signs of damage include holes in the bark, reddish frass, leaf yellowing, and dieback.

Understanding the life cycle and behaviors of root borer beetles is vital for implementing effective control measures. Prevention methods include proper plant care, pruning, and using chemical or biological controls when necessary. Early detection and intervention help reduce long-term damage, ensuring a healthy and vibrant landscape.

Root Borer Beetle Identification

Longhorn Beetle Family

The Root Borer Beetle belongs to the Cerambycidae family, also known as the Longhorn Beetle family due to their long antennae. Some common features of these beetles include:

• Generally brown or black in color
• Long antennae that can be as long as their body

Prionus Californicus

Prionus Californicus, or the California Root Borer, is a species of Longhorn Beetle found in the Western United States. Its distinguishing characteristics are:

• Dark brown or black color
• Antennae with 10-12 segments

Giant Root Borer

The Giant Root Borer (Prionus imbricornis) is another species of Longhorn Beetle native to the Eastern United States. Here are some of its key features:

• Large size, can reach up to 3 inches in length
• Dark brown or black color with greyish-brown wings

Comparison Table

Remember, when trying to identify a Root Borer Beetle, pay attention to the color, antennae, and origin of the beetle.

Life Cycle of Root Borer Beetle

Eggs

Root borer beetles begin their life as eggs, which are typically deposited either within the soil or on host plant bark. Female beetles lay eggs individually or in clusters, depending on the species. An example of a root borer beetle, the Lilac Borer, deposits its eggs on the bark of lilac and privet plants.

Larval Stage

Upon hatching, root borer larvae start feeding on the roots, stems, or bark of their host plants. They are usually whitish and slightly curved. At this stage, larvae cause the most damage to plants by burrowing and consuming plant material. A larva’s feeding period can last months or even years, depending on the species.

Pupa Stage

After feeding and growing in size, the larvae progress to the pupation stage. During pupation, root borer beetles inhabit protective cells within plant tissue or soil, going through metamorphosis before emerging as adults.

Adult Stage

Adult root borer beetles are winged and can fly to locate mates and suitable host plants. Males and females usually mate after emerging from their respective pupal cells. Adult beetles have a comparably shorter life span than their larval stage and do not cause the same degree of damage to plants as larvae. Adult root borers generally feed on plant foliage or flowers.

Key features of the Root Borer Beetle life cycle:

• Egg deposition on soil or host plant bark
• Larval stage involving feeding and significant plant damage
• Pupation within protective cells
• Short-lived adult stage focused on reproduction and limited feeding

Habitat and Distribution

Range of Root Borer Beetle

The Root Borer Beetle, such as the California Root Borer, can be found in a wide range, extending from Alaska to Mexico. Their distribution includes:

• Southwest: They are common in the southwestern United States.
• Alaska: Some species can survive the colder climates of Alaska.
• Mexico: They are found in habitats as far south as Mexico.

Preferred Trees and Shrubs

Root Borer Beetles have a preference for certain trees and shrubs. Some examples include:

• Soil: They generally prefer moist, well-draining soil to lay their eggs.
• Deciduous trees: Deciduous trees like oak trees are often targeted by these beetles.
• Fruit trees: They are known to attack fruit trees such as peach, cherry, and apple trees.
• Brambles: Root Borer Beetles can also infest brambles like raspberries and blackberries.

The table below compares the preferred trees and shrubs of Root Borer Beetles:

The habitat and distribution of Root Borer Beetles are essential factors to consider when trying to manage or prevent infestations in trees and shrubs. By understanding the areas they inhabit and their preferences, you can take more effective steps to protect your plants.

Feeding and Diet

The diet of a root borer beetle is mainly focused on consuming plant roots. They primarily feed on decaying root material and are known for causing significant damage to various plants and trees.

• Eat: roots, fruit, and insects
• Prefer: root material

Root borer beetles have a diverse diet that includes roots of various plant species. Some examples of plants they can attack are:

• Orchards
• Landscape trees
• Shrubs

These beetles may also feed on fruit or insects when they come across them. However, their main source of nutrients is obtained from their consumption of root material. This feeding behavior makes them a problematic group of insects for many gardeners and landscapers.

The key features of a root borer beetle’s feeding and diet include:

• Targeting plant roots
• Consuming decaying root material
• Damaging various plant species
• Primarily preferring roots but can adapt to other food sources when available

In conclusion, root borer beetles have a specialized diet that mainly consists of plant roots. They can significantly impact gardens and landscapes due to their destructive feeding habits.

Infestations and Damage

Signs of Infestation

• Tunnels: Borers create tunnels in the trunk and branches
• Frass: Presence of sawdust-like debris called frass near the base of the tree
• Holes: Small, round exit holes on the bark

Impact on Trees

• Sap Flow: Infested trees may have reduced sap flow, leading to weakened limbs
• Foliage: Affected trees may display yellowing leaves or premature leaf drop
• Susceptibility to Disease: Borer infestations can increase a tree’s vulnerability to diseases

Tree Root Damage

• Compromised Structural Integrity: Tree root borers can damage the sapwood and heartwood, weakening the structural integrity of the roots
• Decreased Nutrient Absorption: Damaged roots have a reduced ability to absorb water and nutrients from the soil

Comparison of Common Tree Borers

Examples:

• The rhododendron stem borer often infests shrubs, causing leaf yellowing and dieback
• Red oak borer mainly targets oak and maple trees, and can be a significant pest in nurseries

Prevention and Control

Cultural Practices

One way to prevent and control root borer beetles is through cultural practices. Maintaining healthy trees and plants with proper care can help avoid infestations. For example:

• Provide adequate water to your plants, especially during periods of rain
• Prune dead branches and remove weak, unhealthy trees

These practices can help reduce the risk of root borer beetle infestations in your orchard or other agricultural crops.

Biological Control

• Woodpeckers are natural predators of root borer beetles and can help reduce their numbers
• Parasitic insects such as wasps can also help control root borer populations

Chemical Control

Chemical control methods should be used as a last resort for root borer beetle management. Some options are:

• Pheromone traps: These can be used to monitor and manage root borer numbers in your area
• Soil injection: This method involves injecting pesticides into the soil near infested trees, but it should only be done by a professional tree care service or exterminator

Remember to always consult a professional before using chemicals for pest control, and follow the label instructions carefully.

References and Resources

The Home & Garden Information Center offers valuable information on wood-boring beetles, including the old house borer, a cerambycid beetle, and its impact on homes. For images and more details on how to identify and control them, this resource is beneficial.

At the University of Maryland Extension, you can learn about clearwing borers, their larvae, and their effect on trees. The site provides insight into signs of damage caused by these insects.

For information on borer insects affecting shrubs, the University of Maryland Extension discusses the rhododendron stem borer and other common beetle borers. You can learn about their impact on cherry laurel and other shrubs.

The Wisconsin Department of Natural Resources is a good resource for learning about the emerald ash borer, an invasive wood-boring beetle. This site offers identification tips, images, and insights into the beetle’s lifecycle.

Lastly, the UC Integrated Pest Management Program provides guidelines on managing the eucalyptus longhorned borer, including information on how to identify, prevent, and control infestations. They also share which eucalyptus species are more susceptible to infestations.

To summarize, these resources provide comprehensive information on various types of root borer beetles, their identification, and control methods. Utilizing these references will enhance your understanding of these pests and help prevent damage they cause.

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 – Palo Verde Root Borer, Derobrachus geminatus: Due for a new name.

Big and Beautiful.
Hiya bugman!
I found this beetle in my garage this evening. We live in Mesa, Arizona. The pic of it with the ruler came out fuzzy, but it’s a little under 3 inches long. That’s about as close as we were willing to get as it has pretty large mandibles. I scooched it along a little to see how it moves, and I think it was asleep because it jolted like I had startled it. It moves slowly and seems feisty, but then it’s easy to get grumpy in this 105 degree heat when all you want is to take a little siesta. I’ve been to about 10 different beetle websites and can’t find it. Can you help? I love your website!!
Sherri

We stand corrected.
Correction
I was just going through the identifications and noticed that someone made an error on an identification: Sheri (Mesa, Arizona) sent in an image of a large long-horn beetle. It was identified as a California Prionus. It is not a California Prionus, but a different long-horn beetle. It is of the genus Derobrachus, and is probably the species geminatus.
Bob Jensen
Entomologist
website:

Update: This just arrived on (08/08/2005)
identifications Hello – I was recently shown your site, and it is excellent. My specialization is longhorned beetles, and in cruising around I notice a number of incomplete or uncertain IDs for this family. I don’t know if you are interested in receiving this sort of input, but if you are, I offer the following additions to your identifications.
The species pictured is what presently is called Derobrachus geminatus, as you speculated– however, for the record, that name has been misapplied, and in fact, the species shown in the photo soon will be given another name.Cheers
Frank Hovore (Prionus) species.

Update: Palo Verde Root Borer
(08/18/2007)
Hello,
I just wanted to let you know that the beetle on your page 2, Some one gave the correct on the family name, but didn’t give a name on what they are called. I live in Tucson Az. & to my knowledge are mainly known here in the SW They are called “Palo Verde” beetles, because the female will lay their eggs in soil surrounding the Palo Verde trees, which will hatch & live underground for 3 years, feeding on the roots of the trees. They are usually seen in the summer & fly in the early evenings, they are attracted to light, which is why we always find them by our front porch where the light had been on! I couldn’t find anything on your page under that name, so I hope you find this helpful. They are the biggest bug I’ll ever want to see with pinchers! I’ve enclosed a couple pictures.Thanks,
Wendy Warunkiewicz

Letter 2 – Palo Verde Root Borer

Subject: What is this critter?
Location: Peoria Arizona
July 25, 2012 9:11 pm
This is not the first time I have seen critters this large. I just would like to know what it is called other than a big black bug.
It is just standing on a standard sized brick so it is a good 3 to 4 inches in length.
Signature: Just wondering

This impressive Longhorned Borer Beetle is the Palo Verde Root Borer, Derobrachus hoverei.  We get numerous identification requests each summer, usually from Arizona but also from other states in the southwest where the host plant, palo verde is grown.  Summer is the time when adults emerge and seek mates.  See BugGuide for additional information.

Letter 3 – Palo Verde Root Borer

Subject: Flying Beetle
Location: Las Vegas, Nevada
June 30, 2012 2:07 am
Have seen about Three of these in Las Vegas, NV in the 12 years I have lived here. I know this one fly’s, as he landed on my neck!
Signature: R. Klaus

Dear R. Klaus,
Summer is the season for large Prionid Borer Beetles and we get reports of various species from different locations across North America.  Your individual is a Palo Verde Root Borer and it is the second example we are posting today.

Thank you! I put him on a tree, hope he’s doing well…

Letter 4 – Root Borer from the Philippines

Longhorn Beetle?

Longhorn Beetle?
Location:  Philippines
September 28, 2010 10:29 pm
We found this bug in our home recently. It was really big. Looking through the internet, I thinks it’s some sort of longhorn beetle. What do you guys think?
Signature:  Ross

Hi Ross,
That is some impressive beetle.  We believe we have correctly identified your Longhorned Borer Beetle in the subfamily Prioninae, the Root Borers, as Ziglipton sanchezi by comparing your images to mounted images on the Salagubang Philippine Beetles website.  Sadly, we are unable to locate any photos online of living specimens.  Interestingly, we did receive another letter today with some blurry images of what appears to be the same beetle, and we will post that letter as well.

Correction: Anomophysis aegrota perhaps
We just received a comment that this may be Anomophysis aegrota, and we believe looks to be a closer match.  It can also be found on Salagubang Philippine Beetles website.

Letter 5 – Palo Verde Root Borer

Beetle
Thu, Jun 25, 2009 at 2:05 PM
A friend found this in her backyard this morning and I went over to evacuate it. It hisses a little and has an earthy oder to it. What kind of beetle is it?
Thanks!
Carla
Florence, AZ

Hi Carla,
Your friend’s beetle is a Palo Verde Root Borer, Derobrachus hovorei.  BugGuide has this information to explain the taxonomy change to the scientific name:  “Synonyms and other taxonomic changes This common and widely distributed species has been called “Derobrachus geminatus”, but examination of type specimens revealed that the true geminatus refers to a much less common species we have called “Derobrachus forreri” (Santos-Silva, 2007, Arquivos de Zoologia, 38:1-94). Rules of nomenclature require that the name geminatus be applied to the less common species (with forreri as a synonym), leaving the common species without a name. Derobrachus hovorei is the new name given to this species, which can be distinguished from true D. geminatus (formerly D. forreri) by its more weakly striolate antennae.
Ted MacRae ”  Though the Palo Verde Root Borer is not dangerous to humans, the adult beetle has very strong mandibles for chewing its way out of it pupal chamber in the woody palo verde tree.  Those mandibles can also give a painful pinch if the beetle is carelessly handled.

Letter 6 – Root Borer

Unidentified beetle
Location: West-central New Mexico, 7100’ elevation, pinyon/juniper forest
July 8, 2011 11:03 am
My husband says it’s a cockroach, I say, no. What say you?
Signature: Mary

Hi Mary,
We hope he is taking you for a nice romantic dinner for winning the bet.  This is NOT a cockroach.  This is a Root Borer in the genus Prionus, and a very likely candidate is Prionus heroicus. It looks like this picture on BuGGuide and though BugGuide has no reports from New Mexico (we would urge you to submit yours) it is found in neighboring Arizona and Utah.  Your elevation might be a key factor in identifying the species.  We like this comment:  “Male individuals of Prionus (Homaesthesis) rarely get this large – the subgenus is distinguished from Prionus (s. str.) by the opaque, non-striolate poriferous areas on the antennae, smaller size (usually less than 30 mm), and less strongly expanded pronotal margins.  Prionus californicus is typically more reddish – the darker coloration of this specimens makes me think it might be Prionus heroicus.  There is no such name as Prionus derobrachus. Derobrachus hovorei is the new name for the species formerly known as Derobrachus geminatus. The species formerly called Derobrachus forreri is the true Derobrachus geminatus.
… Ted C. MacRae, 29 August, 2007 – 11:50am” from BugGuide.  We wondered if this might be P. californicus, but the part of the dark coloration distinguishing the BugGuide photo seems to apply to your specimen, also a male.  An eastern relative, the Broad Necked Root Borer, is our featured Bug of the Month and beetles in this subfamily, Prioninae, have been most plentiful this year.  We would not like to aggravate a male Prionid as they have strong jaws and we suspect some species may be able to draw blood in a human.
P.S.  It looks smashed, so we are tagging this Unnecessary Carnage.

Letter 7 – Root Borer, but what species???

Dasymutilla magnifica? and two more.
Location: Monument Rock, CO, 80132
July 22, 2011 8:01 pm
The was just a little gal, but bigger than an ant and scurrying all over. I had to take 6 pictures to get a good (enough) one. I was tempted to pick up to make her slow down, but given the cow killer post, I’m glad I didn’t!
The second is some mating damsel flies?
The third is a stag beetle? I have never seen such a large flying insect – at least 1.5” without the enormous feelers.
Signature: Dr Lazer – lucky in Colorado

Dear Dr. Lazer,
Your three photos each represent such diverse insect families that we want to deal with them separately.  The beetle that you have mistaken for a Stag Beetle is actually a Prionid Root Borer.  We wish we could make out some details a little better.  At first we thought it might be a Palo Verde Root Borer (see BugGuide) but we have had second thoughts.  We believe this may be Prionus heroicus, which we also found on BugGuide.  The spines on the thorax and the legs both match, but even more importantly, we can only count ten antennae segments and that seems to agree with the image on bugguide.  We researched your location and we know Monument Rock is in central Colorado, and BugGuide lists sightings of Prionus heroicus from Arizona and Utah, which is causing us some doubts.  We will try to contact Eric Eaton to see if he can provide us with confirmation or a correction.

Eric Eaton confirms genus, but not species
Daniel:
There are several species of Prionus in Colorado and it would take too much time for me to go through the research on this.  Some characters needed for ID might not even be visible in the image.  Sorry.
Eric

Thank you so much for your time and effort. You guys obviously do a labor of love of insects and bugs.
I’m attaching a second picture that is head on for antennae detail but don’t feel compelled to spend too much time unless you want to 🙂
This guy when he flies is slightly smaller than a hummingbird since he’s got carapace, wings, legs, and antennae all extended.
And, yes, monument rock is in scrub oak forest at the foot of the front range, 7000′ fasl, west of Monument, CO.
David

Letter 8 – Root Borer from New Mexico

Subject: beetle
Location: New Mexico
June 10, 2014 11:03 pm
This beetle attacked my wife. Lol. Not really but she jumped like crazy. What kind of beetle is this?
Signature: josh

Hi Josh,
This is a Root Borer in the genus Prionus, and based on the shape of the abdomen, we believe she is a female.  Though you joked about your wife being attacked, we should probably warn you that though they do not have venom and are not considered dangerous, the mandibles of Root Borers are very strong and there is a strong possibility that a bite could draw blood, so they should be handled with caution.  This might be Prionus heroicus, which according to BugGuide ranges in Arizona and New Mexico.

Letter 9 – Female Root Borer

Subject: Bug
Location: Central Utah
July 22, 2017 9:02 am
I found this thing this mornin. Thought it was a toy at first. We poked it, and it moved. What is it?
Signature: MeriLowry

Dear MeriLowry,
This looks to us like a female Root Borer in the genus Prionus, and Prionus heroicus which is pictured on BugGuide is a good possibility. 

Letter 10 – Giant Root Borer

Dear Bugman
I found this guy in front of my house I think it’s a Prionus according to other pix I saw on your site. (Great site by the way!!!) But I live on Long island in N.Y. The beetles on your site were west coast denizens.Is this an east coast cousin? Sorry for the poor picture Quality but he/she is black (the western ones on your site looked browner?! I had left my outside light on overnite and I think he crashed ( he was a very cooperative subject) Thanks for your help and again, Great website !!!
Gene & Connor Dolan

Hi Gene and Connor,
Your beetle is in fact a Prionus species, one of the Giant Root Borers. As a group, they range throughout most of the U.S. as well as Canada. Larvae eat live, dying and decomposing trees, shrubs and woody vines. Adults usually emerge in July and August. They are primarily nocturnal and are attracted to lights.

Letter 11 – Giant Root Borer in New Mexico

help!
We found this magnificent beetle on the house the other day. Ran out and grabbed these only photos of it. It was huge. Stayed quite still for it’s photo session. There’s a 5 gal bucket in one photo, as sort of a field of reference for size. The other is a closer view. We live in New Mexico in the foothills and would love to know what this bug is and a little about it if possible. Thank you so much for your help!
Lisa and Ty

Hi Lisa and Ty,
This is a male Giant Root Borer in the genus Prionus. The males of the genus have the signature antennae. We tried to figure out what species this might be on BugGuide’s map page, but they listed no specific species in New Mexico, but reports of the genus in general. Then we found a New Mexico State University arthropod page that lists the California Prionus, Prionus californicus, as ranging in New Mexico. Prionus pocularis is listed in Texas. Your image lacks the necessary detail to make an exact species identification, but we would venture one of the prior two species.

Letter 12 – Decapitated Head of a Root Borer

Devil Ant Head?
Location: Northport, Long Island, New York
August 6, 2011 1:04 pm
Dear Bugman,
We found this insect on my stoop, looks like the head of an ant? Not sure, very curious! Thanks for taking the time to check it out, we look forward to hearing back.
Signature: Best, Mark & Sophie

Dear Mark and Sophie,
This is the head of a Root Borer in the genus Prionus, and judging by the antennae, it is a male.  Since we believe we can rule out the possibility that Lewis Carroll’s Red Queen is lurking in your bushes, the most likely culprit that performed the decapitation is a bird.  Prionus Root Borers are large bodied insects, often reaching more than 2 inches in length.  The soft abdomen is much more palatable than the hard head, and we occasionally receive images like this from curious readers.

Letter 13 – Male Root Borer

Subject:  Giant something in garage
Geographic location of the bug:  North East Utah
Date: 08/08/2019
Time: 11:35 PM EDT
Your letter to the bugman:  I found this thing in my garage. We have an inground pool and do leave outdoor lights on at night.
Should I be scared or should I fryM up?
How you want your letter signed:  Bug Master

Dear Bug Master,
This is a Root Borer in the genus Prionus, and we strongly suspect it is a California Root Borer, Prionus californicus, which is pictured on BugGuide.  Despite its name, the California Root Borer’s range includes much of western North America.  We would not rule out that it might be Prionus heroicus, which is also reported from Utah on BugGuide.  Either way, those impressive antennae indicate this is a male Root Borer.  Root Borers have powerful mandibles, so they should be handled with caution, but they are not considered dangerous.  Many species are attracted to lights.

Letter 14 – Mating Root Borers in Greece

Subject: Big black beetles on Kythera (Greek Island)
Location: Kythera, Greece
June 16, 2014 2:32 am
Hi,
Saw this pair mating on the coast of the small Greek Island of Kythera. The female was 6-7cm long. Any idea what they are?
Signature: Mitch

Dear Mitch,
These are mating Root Borers in the subfamily Prioninae, and we believe they are most likely Prionus besikanus based on images posted to BioLib and the Worldwide Cerambycidae Photo Gallery.  Another possibility is Prionus coriarius also found on the Worldwide Cerambycidae Photo Gallery.

Letter 15 – Palo Verde Root Borer

what’s this bug?
found flailing in our swimming pool in 90+ degree F. two nights in a row in Palm Springs, CA. Maybe it’s totally common, but I can’t seem to find what it is!! (about 2.5-3 inches long, very dark black)
David in PS, CA

Hi David,
This is a Palo Verde Root Borer, Derobrachus hovorei. The increased use of Palo Verde trees in landscaping is probably contributing an increase in sightings of the Palo Verde Root Borer in developed areas.

Letter 16 – Palo Verde Root Borer

Beetle Found by Dog
Hi,
My dog found this crawling on our patio. It is very strong and it was difficult to hold long enough to get a picture. It is about 2 1/2" long from pincer to tail. The color is brown-black. I live in Phoenix Arizona and was found 4th of July night. The pincers are very menacing looking. The legs were going a mile a minute.
Thank You
Ed

Hi Ed,
This looks like one of the Longhorns, Derobrachus geminatus, known as the Palo Verde Root Borer. More information can be found on this site.

Letter 17 – Palo Verde Root Borer

Huge Beetle
I finally found this beetle in one of your 2004 collection… infact, from about a year ago 7/2/04. Since I was willing to get closer to the thing, here are some more pictures of (common name) Palo Verde Root Borer or Derobrachus geminatus.
Darren

Hi Darren,
Thank you for doing our job for us. Glad you located your beetle and your photos of the Palo Verde Root Borer are great.

Letter 18 – Palo Verde Root Borer

Mystery Beetle Las Vegas Found this last July in Las Vegas. It ran right into my face and about scared me to death. He was walking when I took the pic, and I tried to use my free hand as reference for you. He was actually pretty nice and he flew away shortly after.
Danielle

Hi Danielle,
This is one of the Prionid Root Borers in the genus Derobrachus, probably Derobrachus geminatus, the Palo Verde Root Borer.

Letter 19 – Palo Verde Root Borer

AZ desert, large black bug?
Hi there, cleaning out my cement patio today we saw a 2 inch black bug that we think is some kind of cockroach, but this one looked like it had pinchers. Photo attached. Since we move to the northwest AZ desert a few month ago we have seen so many huge strange bugs here and many huge spiders. Can you tell us what it is? Thanks!
Doris

Hi Doris,
The Palo Verde Root Borer is a common Arizona beetle that makes its appearance in the summer.

Letter 20 – Palo Verde Root Borer

3.4inch beetle-mojave
Greetings Mr. Bugman,
I salute your website, for educating so many of us, and taking time to answer so many of our emails. Altho my inclination was to scream wildly and poke sharpt things in it, you’ve convinced me to give that some thought. (smile)
At sundown tonite I was watering the endless garden of the house I just bought here in the Mojave desert, SoCal. Near my foot, tucking out of a hole in the sandy ground I had mistook for a rodent hole at the base of a palm tree and cactus garden, was this bug. He froze when he spied me, but I swatted him away from the hole and leaned a coffee cup over him until I found something to put him in. I thought he was a nuclear mutant roach or water bug initially. And my searches online indicated there were only like 6 species of roach and none came close to this one. Then I found your website, and figured out he had to be a beetle. [S]He is at least 7.5 cm long, 2 wide, has wings. He is shot here in my Trader Joes large 2 lb coffee can. He still lives. I will take it some bio folks at the nearby national park and see who knows what he is and find him a new home. As converted as I feel after trolling about your site for an hour, and my crunchy-bug murderous intent at bay, I have nightmares of them, so he will have to find a new home.
Regards,
Tina
29 Palms, CA
Where the Mojave meets the Twilight Zone

Hi Tina,
What an entertaining letter you have written us. This is a Palo Verde Root Borer, Derobrachus geminatus. You can read more about this beetle on BugGuide. This large beetle is always a cause for alarm when encountered for the first time. Thanks for sending us your image.

Letter 21 – Palo Verde Root Borer

Unknown Bug
Hi,
A friend of mine told me that you could help tell what kind of bug this is. I have found 3 of them so far in my backyard and I have a dog that likes to chase and nip at bugs. I was just wondering if this bug could hurt him or anyone eles that it may get close to. They seem to be active only at night and go dormant at night. And I have seen one fly when out in the open but when confined they just seem to crawl around. Thanks for any help that you could give.
Shasta
Las Vegas, Nv

Hi Shasta,
This is a Palo Verde Root Borer, Derobrachus geminates. They have strong jaws and might draw blood, but they are not dangerous to you or your pet, however, the beetle grubs will bore into the roots of your Palo Verde and other nonnative trees and shrubs.

Letter 22 – Palo Verde Root Borer

Hello,
I just wanted to let you know that the beetle on your page 2, Some one gave the correct on the family name, but didn’t give a name on what they are called. I live in Tucson Az. & to my knowledge are mainly known here in the SW
They are called “Palo Verde” beetles, because the female will lay their eggs in soil surrounding the Palo Verde trees, which will hatch & live underground for 3 years, feeding on the roots of the trees. They are usually seen in the summer & fly in the early evenings, they are attracted to light, which is why we always find them by our front porch where the light had been on! I couldn’t find anything on your page under that name, so I hope you find this helpful. They are the biggest bug I’ll ever want to see with pinchers! I’ve enclosed a couple pictures.Thanks,
Wendy Warunkiewicz

Hi Wendy,
Since that time, we have received numerous other images of the Palo Verde Root Borer that are properly identified. We will include your correction with that long ago entry as an update as well as posting your wonderful images on our homepage and our most recent beetle page.

Letter 23 – Palo Verde Root Borer

three unknown insects
July 10, 2009
I am enclosing three photos of bugs we have found around our Phoenix AZ home. We liv next to a wash and have lots of lizards and birds, and expect to have some insects but two spiders we cannot identfy and now a giant beetle. Can you help us?
Deborah
Phoenix AZ urban neighborhood near wash

Hi Deborah,
We already sent you a quick response identifying your Solpugid and Tailless Whipscorpion, neither of which is an insect, and neither of which is venomous or harmless to you.  The third photo we are happy to post to our site.  It is a Palo Verde Root Borer, Derobrachus hovorei.  According to BugGuide it is found in the  “southwestern United States (AZ, CA, NM, NV, TX) and northern Mexico” and adults are attracted to lights.  Thanks for including the quarter for scale.

Letter 24 – Palo Verde Root Borer

Thanks Daniel!
I hope I can catch a midge in action. By the way, the root borer you posted is a Palo Verde beetle (Derobrachus geminatus). We have lot’s of them in Tucson- they’re HUGE, and they’re really active right now, during the monsoon. I like their fancy spiked collars! Here’s another!
Emily

Hi Emily,
Thanks for the suggestion on the Mexican Beetle.  An expert in the genus might be able to say for sure if it is a different species, but we are taking to the opportunity to post your Palo Verde Root Borer, Derobracus hoverei as its own posting.

Letter 25 – Palo Verde Root Borer

what is this
Location: Surprise, Az
July 8, 2011 12:43 pm
Please Mr. Bugman, tell me what this is
Signature: Southsideirish

Dear Southsideirish,
Your Prionid Beetle is a Palo Verde Root Borer, Derobrachus hovorei, a species found in the arid Southwest where the Palo Verde grows.

Letter 26 – Palo Verde Root Borer

seasonal insect
Location: Wittmann, Arizona, United States
July 8, 2011 10:05 pm
i believe it may be a member of the blister family.
im in Arizona, they come seasonally. they dont swim and they are nocturnal. what could they be??
Signature: Mr. Walker

Dear Mr. Walker,
This is a Palo Verde Root Borer, and they generally begin to appear in late June.  The larvae bore in the roots of the Palo Verde tree.

Letter 27 – Ponderous Borer (including how to differentiate from the Palo Verde Root Borer)

Subject: What is this huge flying bug?
Location: Escondido CA
August 13, 2012 1:43 am
Please help me identify this huge flying bug. I found it at night in my swimming pool. I thought it was dead but after I fished it out it started walking around.
It was ~2.5-3” long and had what looked to be 2 sets of wings.
Signature: Thanks, Matt

Hi Matt,
This is one of the large Root Borers in the subfamily Prioninae.  We believe it is the Palo Verde Root Borer, Derobrachus hovorei and according to BugGuide, they are attracted to lights.  Perhaps the pool light caused this individual to fly into your pool.

Ed. Note:  Suspecting we might be wrong, we get a second opinion from Eric Eaton
Hi Eric,
Seems I have been confusing the Palo Verde Root Borer with the Ponderous Borer lately.  I believe this is the Palo Verde Root Borer.  Can you confirm?
Thanks
Daniel

Eric Eaton provides correction and explanation
Daniel:
Nope, this is a Ponderous Borer.  Note the fine teeth on the midsection (thorax).  The thorax of the Palo Verde Root Borer has very large, prominent teeth, almost spike-like.  You also won’t likely find them together.  Palo Verde Borers are in desert habitats with palo verde trees.  Ponderous Borers bore in coniferous trees, so occur at higher elevations.
Eric

Letter 28 – Palo Verde Root Borer

Subject: What kind of beetle?
Location: Bisbee, Az
July 5, 2013 11:28 am
I found this big guy (or gal) on it’s back at the gas station and brought it home to give it a drink of water and a safe location. It literally appeared to drink for about 30 min. and perked up quite a bit afterwards. I was online trying to I.D. it when I found your site which I’m really grateful for because I’m totally fascinated by bugs & now have a resource for looking them up. I haven’t seen this type of beetle here before. We just started our monsoon season and this is the 2nd type of lg. beetle I’ve seen. I was wondering what it was & what it eats, so I took these photos to send you . They’re a little fuzzy, I don’t have close-up lens. It has a small set of pincers but didn’t act aggressive or try to pinch anything. It mainly just wanted to hide somewhere. Thank you so much for your time and wonderful website ….. I really appreciate it! Janet p.s. I’m really glad you don&#821 7;t endorse extermination!!
Signature: Talks with Bugs

Hi Janet,
This appears to be a Palo Verde Root Borer, Derobrachus hovorei, a species that is common in Arizona.  Here is a photo from BugGuide for comparison.  Adults are attracted to lights, so that probably explains why it was discovered at a gas station.  More information is available on BugGuide where it states:  “Larvae feed on roots of paloverde trees (Parkinsonia spp.).”  The Palo Verde Grub Fact Sheet for Kids states:  “Adult beetles may take nectar ar feed on fruit.”

Thank you Daniel. I do believe you are correct.  I’ve lived in Az 30 years, in Phoenix and south and I’ve never seen one before. Does the Palo Verde Root Borer Grub damage or ever kill the Palo Verde?  Janet

Hello again Janet,
From what we understand, Palo Verde Root Borers do not kill the trees they feed upon.  We suspect that if the Borers are especially numerous, if the tree is already distressed and/or if the weather conditions are especially harsh, the damage might result in significant harm to the trees.

Letter 29 – Palo Verde Root Borer

Subject: Unusual beetle in Arizona
Location: Chandler, az
July 25, 2013 9:48 pm
We have live here in Chandler Arizona for many years. We came home tonight to see this insect possibly chasing a grasshopper.
FYI it was 3 inches long
Signature: Mike

Hi Mike,
Your beetle is a Palo Verde Root Borer, and it is not an uncommon species in Arizona.  You can read more about the Palo Verde Root Borer on BugGuide.  Some wonderful information on the Palo Verde Root Borer can be found on the KCET website.

Letter 30 – Palo Verde Root Borer

Subject: 3 inch Black Beetle
Location: Phoenix Az ( Baseline Rd. and 48th St in Southeast Phoenix)
July 31, 2015 6:03 pm
Hi Mr Bugman or Ms. Bugman: I took a couple pics of this beetle. she was crawling around, either looking for food or to burrow and lay eggs. Could you identify this beetle for me,
Thank You
Paul Carew

Dear Paul,
This is a Palo Verde Root Borer, Derobrachus hovorei.  Based on images on the Small Sunny Garden blog, the pods on the ground in one of your images appear to be palo verde pods, which would explain the beetles presence in the immediate vicinity of the host tree.  We would caution you in handling Palo Verde Root Borers as the mandibles are quite strong and they could deliver a painful bite.

Letter 31 – Palo Verde Root Borer

Subject: Beetle?
Location: Las Vegas Nevada
July 22, 2016 11:42 pm
This gem was sitting by my back door here Las Vegas. What exactly is it?
Signature: Michael Hayes

Dear Michael,
The Palo Verde Root Borer, Derobrachus hovorei, is a large Prionid found in the American southwest.  According to BugGuide:  “Larvae feed on roots of living trees: Populus, Quercus, Prosopis, Ulmus, Parkinsonia, Morus, Citrus, Vitis (Hovore et al. 1987)” and “attracted to lights.”

Thank you. That was what I was thinking. Love this site.

Letter 32 – Palo Verde Root Borer

Subject:  Beetle
Geographic location of the bug:  Green Valley, AZ
Date: 06/27/2018
Time: 12:49 PM EDT
Your letter to the bugman:  Found three of these running and taking short flights around my house after unpacking a tv that a friend gave me.  The item came from Vista, CA, and was stored in a garage here in GV for a couple of weeks.  I caught all three (one at a time) and tossed them out onto my back patio and yard.  Found one dead the next day, but no sign of the others.  Sunday evening I was dumping trash into a large pickup container for collection the next morning and found this one dead in the bottom of an 18 x 18 x 24 deep plastic trash box.  Have no idea where they came from or what they are or were.
How you want your letter signed:  Jim

Dear Jim,
This is a Palo Verde Root Borer, Derobrachus hovorei, which you can verify by comparing your individual to this BugGuide image.  They are native to California, Arizona and other states in the southwest.  They are also attracted to lights, which is possibly why you found them in your house.

Letter 33 – Palo Verde Root Borer from Baja

Subject: Big Baja Bug
Location: Northern Baja California, Mexico
July 24, 2016 2:44 pm
Hi Daniel,
We encountered this big guy coming out of the mother-in-law’s tongue one night in front of our place in northern Baja Mexico. His body is about 2″ long!
Do you recognize him?
Thanks!
Signature: Dana and Alan

Dear Dana and Alan,
This is a Palo Verde Root Borer.

Thanks, Daniel!
xo
D & A

Dana Duff,
I did not realize that email came from you.  If you want more information on the Palo Verde Root Borer, Derobrachus hovorei, you can check out the information on BugGuide where it states:  “attracted to lights” which might explain its appearance if there was a porch light lit.

Letter 34 – Palo Verde Root Borer drowned in pool

Subject: Huge thing I never wanna see again?!
Location: Phoenix, AZ
June 27, 2013 2:34 pm
I just moved to Phoenix, AZ and I am currently house sitting for a friend. The kids and I had been swimming and after I got everyone in the house and dried off I returned to the pool to grab some floats out of it. Floating on top of that water was something that from a distance looked like a small/baby bird. When I got closer I realized it was in fact some kind of huge bug! It eas close in length to the size of my hand outstretched and at least an inch and a half thick in the trunk. Legs were long and thick, even the antennas. It is currently summer here and was about 110 degrees the day I found it.
Please help, I’m grossed out!
Signature: Is it the begining of the end?! Casey

Hi Casey,
It appears to be the end of the end for this Palo Verde Root Borer.

Letter 35 – Palo Verde Root Borer Grub

What’s that bug
Hello,
I found this bug by a Palo verde (Cercidium microphyllum) tree that had just been cut down. It is quite large, latex white, and has 9 black spots on its sides. Each of the first three segments has two small, thornish legs on opposite sides. It is about four inches long, and one inch wide at the head. Help me identify this! It’s the largest bug, much less caterpillar, I’ve ever seen. (Also, it’s a little transparent. I can see a long dark line running lengthwise.)
John
Phoenix, AZ

Hi John,
This is a grub from a long horned borer beetle known as the Palo Verde Root Borer, Derobrachus geminatus. The adults are large eye-catching beetles with strong jaws. We have some photos of them on our numerous beetle pages.

Letter 36 – Palo Verde Root Borers sprayed with nerve gas in California

Mysterious Bug
Location: California
August 2, 2011 12:27 am
Hey guys, I was recently out walking in my backyard and I found this bug squirming on its back. It was an interesting looking one and so I thought I would post it here and see what you guys have to say about it. Every time I flipped it over, however, it would flip itself back onto its back and squirm there. I found another one that was running every which way searching for something. Then, I found another that was lying on its stomach flailing its limbs. After I did some digging, I found out that my neighbor recently sprayed his yard with poison, and apparently these things were caught in the cross-fire. How unfortunate, they are really something special with their size.
Signature: Josh

Dear Josh,
We are taking tremendous creative license with tagging your letter, because generally the person who submits the email is the person implicated in our tags.  In this case, we are charging your neighbor with unnecessary carnage, but not necessarily for just the Palo Verde Root Borer, Derobrachus hovorei, that you photographed.  We don’t know what was targeted by your neighbor, and perhaps he has a cherished Palo Verde tree that was compromised by a larger than usual population of Palo Verde Root Borers.  Adult Palo Verde Root Borers are not the damage producing phase of the insect.  The larvae are the borer and insecticide will most likely not penetrate to the root of the problem.   Sadly, insecticides are indiscriminate in the lives they take, and beneficial as well as injurious creatures may succumb.  Birds and Lizards might also become collateral damage by exposure to strong doses of toxins administered by an amateur.  You may read more about the Palo Verde Root Borer on BugGuide.

Letter 37 – Palo Verde Root Borer, not Ponderous Borer

Subject: Monster bug
Location: Twentynine Palms, CA
July 1, 2012 11:40 am
I occasionally see these monster bugs at night during the summer. I managed to get daytime photos of an injured one. It was on my patio in Twentynine Palms, CA. I’ve seen bigger ones before. I used a metric scal and also a tape measure in inches. Can you please tell me what it is? Thank you.
Signature: Gail McCormick

Hi Gail,
This impressive beetle is a Ponderous Borer, Trichocnemis spiculatus.  According to BugGuide:  “Grubs are found chiefly in ponderosa pine and Douglas fir”

Correction:  Palo Verde Root Borer
Seems we were hasty in our identification and when that happens, we sometimes make mistakes.  Thanks to a comment from a reader, we have made a correction.  See BugGuide for confirmation.

Letter 38 – Probably Palo Verde Root Borer

Subject: Mammoth sized bug
Location: Just outside UNLV in las vegas nv
July 2, 2015 6:29 am
I was walking just yesterday, July1st, in front of unlv in las vegas. I saw this huge bug that appeared dead but I didn’t want to be surprised. It was enormous, maybe 8-10 inches long. I couldn’t imagine seeing this bug flying at me. It is the size of a small bird and I know I would be scared because I don’t know if it stings or not or possibly even bites??? Please tell me there aren’t more of these around.
Signature: Richard Soltis

Dear Richard,
This is one of the Root Borers in the subfamily Prioninae, and we believe it is most likely a Palo Verde Root Borer, Derobrachus hovorei, a species found in many western states where the host tree is found, including Nevada.  Though these are very large impressive beetles, your estimate as its size is quite exaggerated.  BugGuide lists the size as:  “Length, exclusive of mandibles, 54-66 mm” though we have seen images of individuals that approach three inches in length, excluding the antennae.  The mandibles are quite strong, as they have evolved to chew wood, and we believe it is very possible for a bite to draw blood, so they should be handled with caution.

Letter 39 – Root Borer

Beneficial Beetle or Nasty Cockroach???
Location: Las Cruces, NM
May 25, 2011 11:33 pm
Been surfing the web trying to find a match for this guy to no avail. He’s outside my patio door most evenings, although was on the wall in daytime when i took the photo. Kitty plays with him and he makes a squeaky noise in response. Does fly, though not well. It’s almost 2 inches long I think. I’m in Las Cruces, NM. Just not sure if he’s a good guy or a bad guy…
Signature: Shelley

Dear Shelley,
This is a Root Borer in the genus Prionus (see BugGuide), though we are not certain of the species.  Because of the larger antennae, it appears to be a male.  Some insects are difficult to categorize according to the good/bad binary, and we would just have to state that this Root Borer will not harm your home.  Though the larvae bore in the roots of trees, we do not consider them to be an injurious species.  This sighting is earlier in the year than we would expect.  Most reports come in July.

Thank you so much!  I kept looking online last night and was pretty sure it wasn’t a cockroach but still, it’s nice to know he’s not really bad.  It’s been pretty warm here (80s-90s for several weeks), so I guess that might be why. I have also been watering my grass/plants daily and he seems to like that.  Thanks again

Letter 40 – Root Borer

Subject: What is this?
Location: Los Lunas, New Mexico
June 28, 2016 1:28 pm
Hi there. This is the 4th time, I’ve seen this kind of beetle (at least I think it’s a beetle). This is a smaller one I saw, I had a larger one walk in my kitchen about a month ago, but the other night I had one just like this in my bedroom. We’re in the summer now and the weather has been super hot (high 90s). Any ideas?
Signature: Nicole

Dear Nicole,
This is one of the Root Borers in the genus Prionus, but we are uncertain of the species.

Letter 41 – Root Borer Corpse

Subject: Large beetle husk
Location: Jackson, WY
October 21, 2013 10:07 am
Hi Bugman! Love this website… Last Fall I found this beetle husk (empty shell) in Jackson, Wyoming – elevation approximately 6,400’. I believe it could fly, as it looks like it has wings. The actual body, not including antenna, was about 3” long, which is unusually large for this region. I have included photos of the top & bottom of the beetle. Your identification help would be greatly appreciated, as I am including an illustration of it in a book that I am working on about Jackson Hole. Thanks in advance.
Signature: Angela B.

Hi Angela,
These are the remains of a Root Borer in the genus Prionus.  Here is a living specimen, also from Wyoming, that is pictured on BugGuide.

Letter 42 – Root Borer from Brazil

Subject:  who is he little monster
Geographic location of the bug:  Araraquara-São Paulo, Brazil
Date: 08/19/2019
Time: 09:51 AM EDT
Your letter to the bugman:  Hi, I would like to identify these beetles, they were very big sizes about 10+ centimeters. People here are afraid of them and call them “big cockroach”.
Nearby there are eucalyptus trees and lots of sugar cane.
I would like to know if they are rare, because these photos are from November 2018 and since then I have not seen any more here (the first beetle is slightly smaller than the second).
The first question is: are they dangerous?
What is his life time? what does he feed on? and how is his larval state?
How you want your letter signed:  Kainã

Dear Kainã,
This is one of the Root Borers in the subfamily Prioninae, and it looks similar to Ctenoscelis ater which is pictured on Coleoptera Neotropical, but there is no information on the site regarding this beetle’s life cycle.  There is an image but no information on Prioninae of the World.  There is one sighting on iNaturalist.

Letter 43 – Root Borer from Czech Republic

Subject:  Big black bug
Geographic location of the bug:  Czech Republic
Date: 08/09/2021
Time: 12:47 PM EDT
Your letter to the bugman:  Today at 5PM CET we found this guy and we wonder what kind of bug it might be. He was around 5cm long. And his mandibles were pretty big. We tried to look it up ourselves, but not successfuly. Hope you can help although the photos I took aren’t the best quality. Thanks.
How you want your letter signed:  Tess

Dear Tess,
Your beetle is classified as a Long Horned Borer Beetle in the family Cerambycidae, and further subclassified as a Root Borer in the subfamily Prioninae.  We believe it is Prionus coriarius which we found pictured on European Environment Agency which has:  “has very limited information about this species.”

Letter 44 – Root Borer from Namibia

Bug
Location: Windhoek, Namibia
January 18, 2011 4:54 am
Need to know what the name is of this bug
Signature: ?

Dear ?,
This is a Root Borer in the Longhorned Borer Beetle subfamily Prioninae.  They are also known as Prionids.  We are uncertain of the species.

Letter 45 – Root Borer from the Philippines

Identity
Location:  Eastern part of the Philippines, particulartly Dingalan, Aurora Province
September 28, 2010 7:00 pm
Hello! Could you please identify this bug. Would be happy to know the scientific name and common name of this bug.
Signature:  anyway comfortable to you.

Dear anyway,
Your photo is quite blurry, which would have probably made any conclusive identification impossible, but luckily, we received another letter from the Philippines today with correctly focused images of what we believe to be a Prionid Root Borer Ziglipton sanchezi, probably the same beetle you submitted.

Letter 46 – Root Borer Grub

Subject: Giant grub
Location: Foster, Rhode Island
May 17, 2015 8:45 am
I found a two-inch grub digging out an old oak stump in early April, incubated in a jar on the counter for a few weeks (where it grew an impressive two inches) and put it back outside a few days ago. Any clues as to what it might be? I thought about keeping it inside until it hatched but I wasn’t sure I could keep the conditions correct and didn’t want to kill it.
Signature: Earthworm

Dear Earthworm,
This is the grub of a Root Borer in the subfamily Prioninae, but alas we are unable to provide a genus or species.  See this BugGuide posting for a similar image.

Letter 47 – Root Borer: Prionus emarginatus

What is this beetle
I hate to even bother you. Tonight when carrying in the groceries, I had twenty of these come in with me. They are all over the sidewalks and the dirt road in front of the house. My cats were going crazy chasing them. I believe they may be Giant Root Borer, but my daughter whom I home school is not at all sure it matches your pictures. She has taken several nice pictures could you please, if you have the time, verify if this is a root borer or perhaps one you have listed as the mystery beetle. Thank you for your time
Jo and Vicki Petit
Elbert, Colorado
July 2, 2008

Hi Jo and Vicki,
Your beetle is definitely a Prionid Root Borer, and we believe it is the Tile-Horned Prionus, Prionus imbricornis. We will contact Eric Eaton for verification. The hairiness of the thorax is curious. Were the images photoshopped to create the white background? If so, some valuable details like antennae segments might be missing. Your account of the beetle encounter at the grocery store will probably chill some of our readers. Prionid Beetles actually have very strong jaws and can produce a painful, though harmless bite.

Hi Daniel,
No photoshop, it had flown into a white box and my daughter used her kodak digital camera on Macro lens, that was straight out of the camera but cropped down to just the beetle, but nothing more than cropping was done. These came in the house while we were carrying in Groceries (not at the grocery store). They were all over my yard and the road in front my house which is a dirt road and about 20 that came in the house, I am guessing because of the light. They are all about an inch and half to two inches long (the body and twice that with the antennas and legs.) Thank you for your help, Vicki will be very excited that you have answered us, we appreciate your time
Jo

Update: (07/03/2008)
Daniel:
Like you, I am puzzled by the hairy thorax. … There is another genus of prionid (Tragosoma) with a hairy thorax and elytra with similar texture; antennae of Tragosoma are NOT like Prionus. Just to be sure, I will invite Bugguide folks and Entomo-l folks to take a look. Stay tuned.
Eric

Identification: Prionus emarginatus
Hi Eric,
That bug is Prionus emarginatus

Letter 48 – Root Borer from South Africa

Subject: Please could you identify this bug for me
Location: Kruger Park , Olifants Camp
May 19, 2014 2:51 am
While in the Kruger I came apon this bug sitting on a wall in the Olifants Camp, could you please identify it for me.
Thanking You
Mark Adams
Signature: Thanking You Mark

Hi Mark,
This is a Root Borer in the subfamily Prioninae.  The closest matches we could fine are Pseudohovatoma micros on the Prioninae of the World website and Paramacrotoma dimidiaticornis, also on the Prioninae of the World site.  Our initial search did not produce any images of living specimens for comparison.  Another possibility is Macrotoma palmata which is pictured on iSpot, and which is probably our first choice for a correct species identification.

Letter 49 – Root Borer from Swaziland: Tithoes confinis

Subject: Beetle?
Location: North East of South Africa North of Swarziland
January 2, 2014 2:53 am
my niece has taken this picture of a beetle just east of Nelspruit near Marloth Park in South Africa, they would like to know what sort it is, can you help?
Signature: Ken Blackman

Hi Ken,
This is a Longhorned Borer Beetle or Longicorn in the family Cerambycidae, and it is in the Root Borer subfamily Prioninae.  We tried a web search of the subfamily in Swaziland and we were led to this sale on Ebay of a pair of Acanthophorus confinis that are shrink-wrapped, but they looked similar enough for us to try searching under that name.  We next found a lovely image from Tanzania on Le Monde des Insectes, but the genus name was listed differently as Tithoes confinis.  Wikipedia lists its range as including many countries in Africa, including neighboring Mozambique and South Africa, and we believe not listing Swaziland must be an oversight.  We have a six year old posting of Tithoes confinis in our archives.  We are guessing that the grub of this beetle might be edible.

Letter 50 – Root Borer terrorizes Canadienne

Subject: it’s not safe to go outside anymore
Location: Langford, British Columbia, Canada
July 14, 2014 7:10 pm
Hi Bugman,
This was taken today (June 14/2014) in Langford, BC (suburb of Victoria, BC).
It’s HUGE. A kind stranger took the photos for me because I didn’t want to get close. This was a minimum of 3 inches in length – perhaps between 3 inches and 4 inches long. There are dead ten-lined June beetles all over the garage floor (just outside of photo), and they look like ants compared to this monster.
Can you tell me what this is? Does it fly? And when do these start dying off?
I have a hard time enough coping with June Beetles….. discovering this next to my car has has challenged my very being.
Thanks.
Nicole
Signature: nicole

Dear Nicole,
While we fully understand your irrational fears, we feel compelled to try to educate about this remarkable female California Prionus, Prionus californicus.  BugGuide has a noticeable lack of images of female California Prioni, but this single image illustrating the pronounced sexual dimorphism is worth the dearth.  The female is the larger individual on the right in the bugGuide image.  You don’t really need to fear California Prionids, but we would caution you to refrain from handling them with anything less than the utmost care as they have powerful mandibles needed to chew their way quickly out of the trunks and roots they have been feeding within as grubs.  They fly for a maximum six week period in the summer during which time the male’s only interest is finding a female and the female’s only interest is to deposit eggs on a suitable larval food source.  They will not attack you.

Letter 51 – Second Giant Root Borer in 2 Days!!!

Is it a beatle?
Hi Bugman,
This large crawler was ambling through my grass at night when I spotted it. I say it’s a beatle but my daughter who works in the Bronx Zoo is uncertain. Can you tell what kind -and if it is in any way dangerous? Please clue us in.
Many Thanks,
-Les

Hi Les,
This is one of the Giant Root Borers, a beetle in the genus Prionus. It is the second photo in two days from this genus. You could have seen the first photo and identified it yourself had you scrolled down our page. Guess they are early this year since they usually appear in July and August.

Letter 52 – STRIDULATION buggy vocabulary: Root Borer, but which one???

Subject: Large brown chirping beetle?
Location: Albuquerque, NM
July 1, 2012 11:10 am
This big guy flew into the side of my head during a drum circle in the woods that follow the Rio Grande as it runs through Albuquerque. It made a very audible chirp or squeak, in the dark I actually thought it was a bat at first. Others at the circle had seen them before, but we couldn’t find a name for it.
Signature: Raian

Hi Raian,
This is a Root Borer in the subfamily Prioninae and you can see many North American examples on Bugguide.  We believe your individual is in the genus Prionus.  The sound you heard is caused by the beetle rubbing parts of its body together, an action known as Stridulation.  The Free Dictionary online has a nice definition of Stridulation. 

Letter 53 – Tanner or Sawyer Beetle: Root Borer from the UK

beetle
Location: Monmouthshire Wales UK
August 5, 2011 9:43 am
Hi
This chap flew into our kitchen last night attracted by the lights and we have failed to work out what he is. He was at least 2 inches long and gave several nips whilst we were trying to photograph him. It was a warm summer night in rural wales near a stream and river. Sorry the photos are bad he would not stay upright or still.
Signature: Heather

There is no photo attached.

Sorry had trouble sending the request.
Have attached some to this reply I hope.
Thanks for your time and interest.
Heather Morgan and family

Hi Heather,
This is a member of the Longhorned Borer Beetle subfamily Prioninae, and in North America they are known as Root Borers and sometimes Sawyers, though that name can also apply to another group.  We were not aware that any large Prionids lived in the UK, so we became obsessed with finding the identity of your beetle.  After some searching, we discovered the Bioimages UK website and it contained some images of what we believe is your beetle, Prionus coriarius, commonly called a Tanner Beetle or Sawyer Beetle.  The male individual was photographed in Surrey on August 3, 1975.  The Prionids have pronounced sexual dimorphism and the sexes can be distinguished by the antennae.  Your individual is a female.  The Bogbumper website calls Prionus coriarius:  “one of the UK’s largest.”  Zipcode Zoo refers to it as a Sawing Support Beetle.  For a beetled alleged to be found in Europe and UK, there is a surprising dearth of information available on the web, though there are some images.  We cannot help but to wonder if its numbers are declining.

Letter 54 – Tooth-Necked Root Borer

Subject: Giant beetle in our pool
Location: Charlottesville Virginia USA
July 16, 2013 1:40 pm
We just rescued this enormous beetle from our backyard pool. It is mid-summer here and our yard is pretty heavily wooded and in a rural area of western Virginia (shenandoah valley area). We haven’t had any success in finding an identification in any of our bug books or nature guides. Could you help us out?
Thanks, and thank you too for a great website. As a mom of five nature-lovin’ boys, your website is my ”go-to” authority for the kids’ bug hunting discoveries.
Signature: The Hogsed Family

Dear Hogsed Family,
We believe this is a Tooth-Necked Root Borer, Prionus pocularis, based on this description on BugGuide:  “Similar to P. laticollis. More brown, base of pronotum narrower, elytra more punctate, eyes more closely spaced.”  BugGuide also notes:  “Larvae feed in dead pine longs, stumps. Attracted to lights.”  If there was a light in the pool, that is probably a contributing factor to the beetle flying into the water.

Letter 55 – Root Borer from Mexico

Large cranky beetle
August 3, 2009
I found this guy in a new house I’m building in the fron yard, I grabbed him to get a better picture, with a better sun exposition, but it got really mad at me, so that when I let it free, it was chasing me really fast and it was very difficult to get the camera to focus and I guess it most be still looking for me somewhere.
Do you know what type of beetle it is?, it was around 4 in long.
Jorge Farias
Jalisco Mexico

Hola Jorge,
This is a Root Borer in the subfamily Prioninae, but we are not certain of the species.  Hopefully, one of our readers will be able to supply an exact species for us.

Thanks Daniel!
I hope I can catch a midge in action. By the way, the root borer you posted is a Palo Verde beetle (Derobrachus geminatus). We have lot’s of them in Tucson- they’re HUGE, and they’re really active right now, during the monsoon. I like their fancy spiked collars! Here’s another!
Emily

Hi Emily,
Thanks for the suggestion on the Mexican Prionid.  We agree that it is a Derobrachus, but there are other species of Derobrachus in Mexico and we are just not certain that this is a Palo Verde Root Borer or perhaps one of the  others, like possibly Derobrachus sulcicornis.  Jalisco is in central Mexico which supports our theory that this may be a different species.  Since insects do not respect international borders, if this submission had been from Sonora or Chihuahua, we would say the Palo Verde Root Borer would be a more certain possibility.

Update from Eric Eaton
August 4, 2009
Hi, Daniel:
I agree with the identifications for both of the beetles:  A species of Derobrachus, and an example of the “lion beetle” as offered by others.  See what a great community you have created?:-)  I tell you, I learn as much from WTB as I contribute….
… Keep up the great job, Daniel:-)
Eric

Letter 56 – Unknown Root Borer from Tobago is Callipogon armillatus

What bug is this please?
August 12, 2009
From Tobago, West Indies. I have another image without my hand in the picture if you would like it. The hand is for scale.
Mr. Sticks
Tobago, West Indies

Dear Mr. Sticks,
This is a Root Borer Beetle in the subfamily Prioninae.  It resembles the North American beetles in the genus Derobrachus, but we have been unable to quickly unearth any possible species matches in Tobago.  Perhaps one of our readers will have better luck in the species identification.

Daniel:
This looks like Callopogon (=Enoplocerus) armillatus. The common name appears to be Giant Longhorn Beetle; appropriate for one of the largest Cerambycids (up to 12 cm!). It ranges from Panama to northern Argentina, including Trinidad and Tobago. As you say, it is a root borer (Cerambycidae: Prioninae). Regards.
Karl