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

Palo Verde Root Borer

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.

16 thoughts on “Palo Verde Root Borer”

  1. One of my co-workers thinks he found one of these guys in El Cerrito, CA (Northern CA) at a school were I teach. I think that we’re way too far north and there are no Palo Verde trees up here. What do you think we might have found?

    • There are many relatives in the subfamily Prioninae that look quite similar and several are found in Northern California.

  2. The big summer monsoons have began here in Arizona. The last major dust storm which blew through a few weeks ago, brought a huge beetle like the one pictured above. A few days later after that night, I found one floating dead in the pool. I am terribly afraid of most any beetles, especially those which resemble cockroaches (we have HUUUGE ones which get bigger the closer to the mountains which are everywhere in Arizona)! I was besides myself and can’t bring myself to look at them.

    I have no idea why I have this phobia because I am typically a person that tries to save these small life forms instead of giving them the snapper. It is different with what my mind thinks are cockroaches. Then I go into survival mode and look to give them the STOMPER! It is a fight or flight mode, unless it’s NOT a roach. These things do not move like roaches (they are actually pretty slow, but I don’t know if they have a fast mode) and I really didn’t get the feeling they were, but they are ENORMOUS!! They seem to be more a beetle than a roach. That’s why I came searching here.

    I found ANOTHER one just yesterday in the afternoon. It was hanging under the overhang of the house, staying out of the sun. I knew the monsoons blew them in or they flew over from the many palm trees we have around here (and Palo Verdes) due to the weather. The house is stucco so it gives plenty of surface to hang on to (two stayed on the house, one died in the pool). Like cockroaches, these bugs seem to be subterranean because we rarely see them hanging out. There are a lot of crickets around the house, but honestly, I’ve never seen a cockroach or closely related cockroach-like beetle (I forget the name of the kind that live outside and root beneath the dirt – Oh yeah! Palmetto Bugs!) around here. Maybe the cricket population gets them first?

    Anyways, I was concerned about health (my youngest is very allergic to cockroaches) if these were a similar type of bug. From the sounds of it, they are part of the ecosystem of the Palo Verde trees. As I stated, possibly they get blown about in the big dust storms and monsoons so common here in the dry Southwest. Almost like a forced migration if they come out this time of year. Thoughts?

    • In our opinion, the monsoon conditions have triggered the emergence of the adult beetles which have awaited the ideal weather conditions in the pupal stage. We do not believe they have blown in.

      • I see. Apparently your group is not from the Southwest and don’t know how powerful dust storms (which raise HUGE walls of desert sand and dirt) can be. I read a blog ( for reference) that described the night raids of these beetles during their mating season. To understand, the movement of the beetle doesn’t have to rely on its own short cycled life span once above ground. It is very possible they are lifted after coming above ground by these torrid storms.

        Since you guys are experts in the entomology arena, maybe you should do a bit more research on other environmental affects which impact the life cycle of such creatures. I wrote a plethora of info in descriptive, your answer was redundant and gave no new information (opine doesn’t matter much when facts are requested) since I already notated they could have come from a neighboring eco-shelter like a palm tree or adjacent Palo Verde. We have a 12,000 square foot lot with no Palo Verdes in our yard. None of the neighbors do either. Most everyone in the entire neighborhood has pools and pleeeeenty of Palms. The bugs are simply not fast enough to have walked here and they need to be around others to mate (I would consider that they’d like to be in the vicinity of Palo Verdes to do so since they only have a month to live).

        Hmmmm??? Seems like I answered my own question.

        At this optimal and active part of the year for the Root Borer Beetle to our native Palo Verdes, seems, at least according to some sources, they get blown around quite a bit. Maybe they blew in from an adjacent neighborhood (This one is 30 years old and I haven’t ever seen them here) that has an active Palo Verde population of beetles. All depends on the landscaping design. Palo Verdes are not a part of the immediate neighborhood (which hosts relatively spacious lots), but there’s a resort, adjacent mall, corporate sector and other landscape designs nearby which I’m sure host Palo Verdes. Maybe a little more research would have proven a better answer from the experts. I thought this was a fact based site and that’s why I posed my question here. Anyone else have more info?

        • Thank you for pointing out our numerous shortcomings and sharing your annoyance with our readership. One of our biggest annoyances is being chastised for providing free information to the web browsing public. We can see by your lengthy response to our opinion that you are not ready to end this dialog, so we will proceed with a more thorough response for you.

          First, we should clarify that we are not entomologists, nor are we experts in entomology. What’s That Bug? has always been an art project. Our degrees are in Fine Art, though it has always been our mission: “to promote an appreciation of the natural world around us, especially a tolerance of insects and their relatives.”

          In your original comment/request, you stated that you are “terribly afraid of most any beetles” and though we are not medical experts qualified to dispense medical advice, we are aware of entomophobia, which is defined on the MedicineNet website as: “An abnormal and persistent fear of insects. … A true insect phobia is defined by a persistent irrational fear of and compelling desire to avoid insects, mites, spiders, or similar phobic objects and significant distress from the disturbance despite recognition by the phobic person that their fear is inappropriate, unreasonable, and excessive.” For this phobia, we would recommend that you seek professional treatment. Again, since we are not qualified to dispense medical advice, we suggest you seek the appropriate medical opinion regarding your concerns about health and allergic reactions of your children.

          Your original comment/request demanded a great deal of speculation on our part. You did not provide an image to document your sighting and you were requiring a leap of faith on our part to even confirm that you encountered a Palo Verde Root Borer when you yourself admitted you thought it might be a cockroach. In addition to the Palo Verde Root Borer, other members of the subfamily Prioninae, which feed on other plants, are found in Arizona. These include the Ponderous Borer which is represented on BugGuide, the Hardwood Stump Borer which is represented on BugGuide, Tragosoma chiricahuae which is represented on Bugguide, the California Root Borer which is represented on BugGuide and Prionus heroicus which is represented on BugGuide. Without a high quality image, it is impossible for us to determine the exact identity of the insect you encountered, which may be one that feeds on some tree that grows in your immediate neighborhood.
          The Palo Verde Root Borer and other related Prionids are capable of flight, as are some species of Cockroaches. Once airborne, it is entirely possible for them to be buffeted about by the wind and even carried several miles. One does not need to be a resident of the Southwest to understand that wind blows things about, and in the case of tornadoes and hurricanes, it is possible to transport airborne objects many miles from their point of origin. We should have clarified in our original opinion that we believe the creatures you sighted were local and that they were not transported from hundreds of miles away on monsoon winds. We understand fully that property boundaries, even those on 12,000 square foot lots, do not prevent organisms and inanimate objects from blowing in on the wind.
          Those are our thoughts. Also, we do not believe your cricket population is a factor in your recent sighting, which may or may not have been a Palo Verde Root Borer. We hope we now have provided you with some answers that you would not have considered yourself.

  3. Thank you kindly for your thorough response. I see…Artists. I am your readership as well. Your comments will help me create a better request if I should use your site as I have on various occasions prior.

    I never said I hurt bugs or am overly fearful. Just beetles due to associating them to the disease weilding cockroach. As well I try to educate myself by researching and learning so I am not unnecessarily reactive. The very clear photos were a wonderful teaching tool for me to determine the 1,000% probability (forgoing a DNA test for bugs, lol and joking) it is a PVRBB. Also, I only mentioned that crickets eat cockroaches. The roach is a bug I react to, mostly due to fight or flight. That was my whole point of writing, to make sure I didn’t harm something of absolutely no threat to us. The PVRBB does scare with its ominous looking “presence” and massive mandibles, but can’t hurt us disease/contagion wise.

    So point well taken: I’ll be more clear and not expect the people who give these answers for free to do all the work. Sorry for the public flogging on both sides. It wasn’t my intent to injure your community. Please accept my apologies.

    • The Palo Verde Root Borers do not carry diseases to humans, though we can’t comment on the possibility of them spreading pathogens to the trees they feed upon. For the record, Cockroaches are allegedly quite clean, though they do have a reputation for spreading filth. Beetles and Cockroaches, though they share some superficial physical similarities, are not closely related to one another. Cockroaches are actually most closely related to Termites as they are in the same order, Blattodea. Crickets are opportunistic, and we imagine they will take advantage of dead or dying Cockroaches as food, though we have not heard of any documentation of Crickets preying upon healthy, fully-grown Cockroaches. Also for the record, DNA testing is the only certain way of ascertaining the true species identities in some genera of butterflies that all look very similar.

  4. Thanks, Bugman, all useful info here in the SW where there is an abundance of all of those. My little one and I especially like the butterflies! You guys take care. We’ll see you all on our next bug expedition!

  5. Wow…I just thought this was a fun place to bring my grandson to try to spot the bugs we see in the yard. I was content until I found out you guys aren’t 10000% accurate…but thank you for appeasing us to now. Oh this doesn’t mean we’ll be leaving!!!…We’ll just know you aren’t 10000% accurate…huh

    • We make many mistakes, but they aren’t generally too far off the mark. We depend on the huge internet network of insect experts to assist us.

  6. Well we come and we so appreciate you! This is an awesome site and very informative.
    ANYONE can make a mistake and yes, there are other places we could search but this one is friendly and beautifully done. Thank you! : )

  7. Bugman, I think I love you. I find folks who do things for the sheer joy of helping others to make up a large majority of the people I choose to interact with. Thanks.


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