Palo Verde Beetles

It’s that time of year again!  Time for the palo verde beetles to descend on Tucson and fill the night sky with giant beetles flying around drunkenly looking for mates.  I already wrote a post about how much I love these beetles and promised to write more about their biology.  Today I am making good on that promise!

Meet the palo verde beetle (or palo verde root borer beetle), Derobrachus hovorei:

palo verde beetle top view

Palo verde beetle

I think these beetles are one of the best parts of living in the Sonoran Desert.  Each summer when the monsoons begin, these beetles start to appear.  They’re large, dark brown nocturnal beetles, 3 – 3.5 inches long.  Check out the long, luxurious antennae:

palo verde beetle antenna

Palo verde beetle antenna

Palo verde beetles belong to the beetle family Cerambycidae, the longhorn beetles.  You can see how the family got its common name!  Nearly all members of the group have these long antennae, including several important wood pest species (such as the Asian longhorn beetles).  The palo verde beetle is no exception.

I think the palo verde beetles look rather fierce.  Check out the spikes on the thorax:

palo verde beetle thorax

Palo verde beetle thorax

And the big pinching mouthparts (called mandibles):

palo verde beetle jaws

Palo verde beetle jaws

In spite of their size, their armor, and the powerful jaws, these beetles are largely harmless.  That’s not to say that they won’t flail about wildly and try to bite you if you pick them up, and they can deliver a strong, painful pinch if you’re not careful.  (That’s never stopped me from picking them up!)  Mostly though, the beetles use those impressive mandibles for fighting and/or mating.  I posted a photo of a male and a female palo verde beetle struggling with each other before they mated a while back and jaws were used extensively as the male subdued the female.  In fact, she lost a leg and both antennae in the struggle.  Those strong jaws are also used by males in battles with one another to win females.  The better fighter a male is, the more females he has a chance to mate with.

There’s one thing the jaws aren’t used for though: feeding.  Adult palo verde beetles don’t feed at all and rely on nutrient reserves they ingested as larvae to fuel their adult activities.  As result, their adult lifespans are pretty short, less than a month.  During that month, they fly around (not very well and in the dark – there’s nothing quite like seeing one of these flying toward your head at night!), fight, mate, and lay eggs.  That’s a lot to do for a large flying animal that doesn’t eat!

Once a male finds and mates with a female, the female will burrow into the soil at the base of trees and lay her eggs about a foot down.  When the eggs hatch, the larvae feed on the roots of the trees, focusing on the starches within the roots.  After 2-3 years of feeding and growing, the larvae are enormous and look like this:

palo verde beetle larva

Palo verde beetle larva! This one was over 3 inches long.

The larvae have strong and powerful mouthparts too, essential for cutting trees roots open so they can eat.  When they’ve grown large enough, they pupate underground.  The adult emerges when the monsoons arrive and dig their way up to the surface, leaving large round holes around the base of the tree where they grew up.  Then they go about the serious business of flying around in the dark (scaring a lot of people in the process), looking for mates, and starting the whole process all over again.

Palo verde beetles get their name from the palo verde tree, a gorgeous desert tree with green bark native to the Sonoran Desert.  If you dig up palo verde trees, you will supposedly nearly always find several palo verde beetle larvae happily munching away on the roots.  Because they are root borers and root borers are commonly associated with dead, dying, or unhealthy trees, palo verde beetles are often considered pests.  If you search the internet, you’ll find all sorts of crazy ideas for how to rid your yard of these “dangerous” beetles so that they don’t kill your trees.  It all a bit sensationalistic though!  Palo verde beetles DO eat roots of trees, but consider this: there are millions of palo verde trees in the Sonoran Desert and nearly all of them have several palo verde beetle larvae gnawing on their roots.  If the beetles are really destroying tress, wouldn’t there be fewer palo verde trees around?  Palo verde beetles can cause some damage to trees, especially non-native ornamentals, but usually only in trees that are already having problems.  The best defense against palo verde beetle damage is taking care of your trees!  If you keep young trees healthy by watering them regularly and fertilizing, they will usually be able to withstand palo verde beetle larvae eating their roots quite well.

While I completely understand why people might be scared of these lumbering, giant beetles – they are VERY large after all – I can’t help but love them!  I associate them with lazy, hot summers and the arrival of the much-needed rains.  They’re hilarious to watch flying around.  And they’re stunning!  As proof, I leave you with this last image:

Palo verde beetle side

Palo verde beetle, side view

Love ‘em!

_______________

Unless otherwise stated, all text, images, and video are copyright © TheDragonflyWoman.com

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67 thoughts on “Palo Verde Beetles

  1. Great write-up and pictures! Makes me want to get to the desert to explore even more!

    One minor thing though; emerald ash borers are in the family Buprestidae, not Cerambycidae. Still a major forestry pest, just the wrong family.

    • Agh! Of course! I knew that – even wore an EAB temporary tattoo around an Ent Soc meeting a while back. This is what happens when I stay up until 3AM writing blogs posts. :) Thanks!

  2. These are impressive. I love all types of Prionids. They are just fascinating. The Palo Verde Root Borer is among the greatest of the Prionids in my opinion… Right below Macrodontia spp and Titanus Giganteus. I’d like to get a couple myself. Do you sell/trade? I’d like to have at least one that is over 2 inches in my collection (I have like mostly 1 1/2 inch Prionids found right here in SC). Arizona has such amazing insects…

    Well, keep up the posts. This is a great blog.

  3. Are they usually found in California? We live in Galt Calif. Just South of Cali’s capital, Sacramento. My children found a large dead one today.

    • I know they extend into California, but I’m not sure how far north they go. There are several closely related species though, including other Derobrachus and the very similar Orthosoma. The prionus beetles look a lot like them too. It could be one of them too. If you really want to know what it is, I recommend submitting a photo to bugguide.net (click on ID request at the top of the page to get started) or take the specimen to your local extension office. The extension office should have an entomologist on staff, or at least Master Gardeners, who can help you with the identification.

  4. I pulled up a small tree stump in my yard here in Las Vegas and found one of those humongous larvae, put it in a giant plastic cup from a fast food joint with some of the dirt from the hole from which it came. Dragonfly Woman’s pic doesn’t show the hideousness of the mug of this larvae and it’s big chewing chompers. I couldn’t believe it when two days later I checked on it and it had chewed/bored a hole through the bottom outer edge of the cup. I kept the cup, and it shows the miniscule chew marks where it tried in various place in the cup before it settled in to finish it’s way through. The hole was at least an average of .250 inch!
    The same day, I caught an adult, and Zplock (r) bagged it and speed froze it in my freezer. I am thinking of putting it up on ebay for sale for someones research or bug collection. I wish I’d have known the jaw power of the larvae, I would have speed frozen it too!

  5. I have a palo verde and it has small holes on all branches they are in grups 4holes or 6holes and they are about 6″ apart , I don’t see any holes in ground so I don’t think is the paloverde borer . What can it be? Please answer thank you

    • The palo verde beetles wouldn’t be eating the branches of your tree even it does have them, but I’m not sure what else it would be. I work on aquatic insects, so your question is a bit outside my area of expertise. You might try calling your local Master Gardeners. They would be more likely to have an answer for you.

  6. I live in NJ, and believe it or not, a borer beetle, about 3 inches long, got into my house last summer. I do have a sickly tree right next to my house. I never saw or heard of them before so it came as quite a surprise when I was awakened in the middle of the night by a small flying chihuahua, zipping about in the dark, slamming into things and falling. The sound effects were startling! After searching with the lights on, I thought I’d find something I might have seen before… During the week that followed, I found a few more, having drowned in my pool. The whole summer, I slept with one eye open. I can not stress enough how I truly DO NOT appreciate this natural wonder (or most bugs for that matter). I can not afford to prune the tree (once struck by lightening), to help it regain its health… so the borers are going to town on it. Not happy & rather grossed out. Hoping I can somehow get rid of them before they destroy the tree, or move in with me.

    • Sorry you’re having a bad experience with them! All I can say is that the beetles are probably only hurting the tree at this point because it was doing poorly enough that their nibbling on the roots is actually stressing the tree. Most borer beetles eat to their heart’s content without causing any real damage so the tree was probably on its last legs anyway. But, you should talk to someone in your area for more specific information about what you can do about it. I recommend contacting your local extension office (the master gardeners can probably help!) or a good arborist. They’ll be able to give you specific, local advice on how to save your tree, if possible, and take care of your beetle woes.

    • It won’t live more than a few days most likely as they don’t feed, but preserving it is easy! Just position the legs how you want them to look and then leave it alone for a week or two. The innards will rot/dry and you’ll be left with a nice specimen!

  7. I live in Phoenix and this week I found two inside my house!! They are nasty and scared the heck out of me ! How do they get in? I need to block the entry site so more don’t come in.
    Daphne

    • It’s a little unusual to find them indoors, but I would bet they’re either coming in as you go in and out at night (especially if there’s a porch light near your door, or they’re sneaking in to find a place to sleep during the day. Sorry you’re getting them in your house though! I only ever had them in my house when I brought them in intentionally to photograph them. It would be a little intense coming around a corner and seeing one sitting there on the carpet!

      • I live in Tucson, and true to Monsoon season, there are so very many of these guys bobbling around outside and, despite a lack of general beetle love, we live in harmony.. Last night, however, I experienced a whole new level of horror. For some reason, they found a hole in the roof over my AC closet, and in the space of about 15 minutes 10-15 of them (at last count!) bumbled into my house and began flying around, landing on our couch, table and even into our kitchen. After we hurriedly closed the door to the closet, there was still an unknown number of them in there trying to get under the door, waving their antennae. We blocked the door more securely, top and bottom, and ushered the others back outside using a broom, yardstick, and phonebook. It was almost like a swarm of them.. Do you have any idea why they might try to get, en masse, like this? I’ve never heard of anything like it! I don’t hear them in the closet anymore, so I’m assuming they’ve died. Were they trying to burrow?

        • Wow, what a crazy experience! I have NO idea what they were doing. Maybe trying to find a place to lay eggs (though they normally lay their eggs near palo verde trees, hence the name palo verde beetle)? They’re attracted to lights, so maybe they were just headed for the lights indoors? Or maybe they were just following the cool air? Anything I could tell you would be pure speculation! I think even I would have been a little weirded out by having that many crawling around in my house though… Here’s hoping it doesn’t happen again!

  8. My daughter found one of these big guys wandering around in the driveway last night. And we live in Idaho. I have done some reseach and these things are not supposed to be found here. We are in the desert SW corner of the state, so quite near the Nevada border. I know bugs don’t recognize state lines, so if they are found in northern Nevada, they could easily make their way here. Should I make the local extension office aware that there could be a new bug in the state? Or is it not enough of a “big deal”? And BTW, I don’t have a single tree (only sagebrush) on all of my ten acres, or the surrounding 1000 acres either, so I have no idea how the poor thing would ever survive here.

    • There are several closely related species to the palo verde beetles and some of them should make it into your area. The Prionus beetles are similarly sized and shaped, so I’d bet you saw one of those. They’re very widespread. Did you get a picture of the beetle by any chance? I’d love to see what it looks like!

  9. Thanks for the information. I found one of these on its back on the ground after a storm (in New Mexico just east of Albuquerque) and had never seen one before. Being an elementary school teacher, I think it is really important for children not to see all insects/bugs as “icky” so I keep a pair of purchased Madagascar Hissing Cockroaches on my desk and have bought Bess Bugs, and African Millipedes. When I found this Palo Verde fella, my first thought was to keep him/her to show my students, but now I’m not sure I should, especially if he hasn’t mated yet. hmmm… Any advice? Thanks.

    • Ooh, tough call! Keeping it means a great new experience for your students, and that’s often a good thing. Are your kids in school now though? These beetles only live a few weeks, so if they’re not back in school until August you’re most likely going to be showing them a dead beetle…

  10. That’s what I was thinking, too. Don’t want to show them a dead beetle. I have it (Ringo) hanging in my kitchen in a large mesh butterfly habitat (which my husband sort of sighs at when he walks by – ha ha ha). School doesn’t start for another few weeks. Think I might set him free to do his business. Thanks again!

    • Yeah, it’s not going to survive multiple weeks in captivity for sure because they don’t eat as adults. As much fun as it would be to show your students, if it’s going to be that long it’s probably best to let him go his own way.

  11. Hi! I just met one of your friends Root Borer, I live in Maryland and he was on my garage door, because I didn’t want him to get hurt and I also didn’t want to get hurt I put him in a washcloth and moved him to a plant, to my surprise he started singing with his back legs. He was just lovely I got a picture of him if you want to see him. I came home tonight about 8 hours after my first encounter and low and behold he’s back on the garage door O_o

  12. Oh, @dragonflywoman, there’s this giant sized black one – a full 3.5 “, I’d say, that we found last night walking in the backyard, along the patio! Not quite sure how to deal with it, we covered it with the closest thing at hand – a small empty pot (awaiting to house a plant) – hence with a hole at the base (no need for the beetle to bore one). ;) Of course searched the internet to hone in on the AZ species (from the 250-350K varieties in existence I believe!). My spouse is fascinated; I’m grossed out. It’s now morning, and he replaced the pot with a glass square vase, so we can see what’s going on, and to actually be able to see the creature. He reminisces his childhood days when he’d poke around with all similar ‘little’ fellas. (I’m not amused). We want to let this Borer go… plenty of Palo Verde in the neighborhood – none in our backyard. We do have some young bamboo recently planted in pots. Am not quite certain yet how to deal with the situation. Oh, while writing this, can see him pottering around trying to figure out a way! All these scientists (I was a science grad too… give me Chemistry or Botany any day, Gee)! I’ll try taking a pix. Cheers.

    • If the beetle’s that big, out at this time of year, and from Arizona, it’s almost got to be a palo verde beetle! They don’t feed as adults, so they don’t live very long. Keeping it trapped will likely result in a dead palo verde beetle in a few days. If you haven’t done so already, I recommend releasing it. It’s not going to attack you or anything, so you’d just lift the vase off and let it go about its business.

      I think they’re amazing beetles! It’s well worth a good look. They’ve got all kinds of intimidating looking spines and beautiful eyes – gorgeous beetles if you give them a chance!

  13. Pingback: Giant Black Beetle… Palo Verde Beetles « Words-n-Motion

  14. Do they “hiss” at all? I have a friend that said her babysitter found what sounds like a Palo Verde beetle in the house (children’s playroom) and it was hissing. Needless to say, they are all freaked out.

    • I’m trying to think what the sound they make sounds like. Not really a hiss and I’m not exactly sure how they even make the sound, but they can make a sound for sure. They don’t like being backed into corners or messed with, so it wouldn’t surprise me if one that made its way indoors was doing everything it could to look menacing.

  15. Thanks for this informative post and fabulous pix! Just found one of these guys in my backyard, getting paddled by a neighborhood Tomcat! I shared your page on FB.

  16. It’s May 23rd 2013 in Palm Desert CA and I have been pulling these out of my pool the last couple days. They apear to have drowned but if you take them out they reanimate in a couple hours and usually end up back in the pool, not sure why since I don’t think they drink. They are pretty amazing, there underbellies kinda look like palmeto bugs aka cockroaches. Creepy looking but very cool.

    • I think they’re amazing creatures, so I’m glad that you think they’re cool! Odd that you’re finding so many in your pool though. Wonder if they might just be at the end of their lives or are attracted to light reflecting off the water or something…

  17. Hello:

    I need to know how to overcome my fear of these things. Can you offer any suggestions? I think I need to go into therapy!

    Thank you…

    • That’s the first time I’ve ever gotten this question! Not sure how to solve your problem though… Perhaps you can at least take comfort in the fact that they’re not around for very long each year?

  18. it’s the 22nd june 2013 and we have hundreds of these beetles flying around the area. We live in Valencia, Spain (east coast on the med.) I’ve read up on these cool dudes but all websites only mention america. These are definately in spain too I can confirm. They really are cool to watch flying. I always think of james bond with his jet pack on his back, they look like they have jet packs on with their legs dangling down when they fly. I’ll try and video it if I can. They also make a high pitched squeal when you pick them up. I have even hand fed one with a piece of apple, they can be very tame and trusting. Shame they only live a month, they could make cool pets. :-)

    • The palo verde beetles are wholly an American species, but you might have something very similar in your area! The longhorn beetle group is a big one and many of them look like the palo verde beetles. Interesting that you saw so many of them at once. Cool!

  19. they are gross and i hate them. they look like a huge cockroach more them a bettle. they look like florida palmetto bug

    • I could see how you might think they look like palmetto bugs! But if you want a good laugh, watch a palo verde beetle fly sometime. It’s much less coordinated than the palmetto bugs, and they swerve all over everywhere when they fly. It’s pretty pathetic!

      • I’m pretty certain that one of these Palo Verde Beetles in under a glass on by bathroom floor. I have no earthly idea how the 3+” creature got into my 2nd story condo but it’s not welcome here. If one is in here…what is the likelihood of their being more? I may not sleep tonight!!
        I have a picture of this scary beast. How can I share it with you so you can help me identify it?

        • Send me a message in the Contact Me form on my blog and I’ll get in touch with you about IDing it. You are unlikely to have more than one in your house at a time though, so I wouldn’t worry about having more!

  20. I lived in the southern part of Michigan, and I know this is odd but a few years ago while living out in the country I went out at night and happened to see this big black thing on the ground among the stones in the drive-way. Upon closer inspection I realized it was a HUGE (big to me and bigger than anything I’ve seen up here before -several inches long, about 3/4″ and about an inch wide if I remember right) beetle. I had never seen anything like it before, I ran inside the house to get something to put it in so I could do some research on it and find out what it was but by the time I returned to the spot it was in it had vanished. I tried and tried to find out what this insect was and failed until today when I read a post from HuffingtonPost about the Palo Verde Beetle and as soon as I seen it I had no doubt that is what the insect I had seen was as it looked exactly like the one among the stones in the driveway. My only question is, how would such an insect make it’s way up to Southeastern Michigan when according to everything I’ve read, they live in Southwestern parts of the country i.e. AZ, CA.?

    • I suspect it was a close relative of the palo verde beetle! There are several very large beetles that look similar in the same group, so that would be my best guess. Orthosoma brunneum would be a likely possibility as it looks very much like the palo verde beetles and is also in your part of the country. Want to look it up on BugGuide.net and see if it looks right to you based on what you saw?

        • No, you can’t add photos here. Are you on Facebook? You could upload the pic to my The Dragonfly Woman page there if you’d like, or shoot me an e mail via the Contact Me form, link at the top of the page, and I’ll give you an e mail address where you can send the photo.

  21. I found one on my back porch in a spider web here in Mesa. Took me 2 weeks to find out what he was and where he came from.I have lived here since 1976, first one I ever looked upon. Scared my wife half to death. Nice bug , no doubt.

    • They do seem to be less common in the Phoenix area than in Tucson! It’s hard to miss them further to the south, but I know some entomologists and bug enthusiasts in your area that get REALLY excited when they see one because they’re not that common. Sorry it scared your wife (my husband is right there with her, I assure you!), but I’m glad you enjoyed it at least!

  22. Excellent article! I’ve lived on the Arizona desert for almost seventy years and seen those beetles and never really knew what they were until now. We always called them “Japanese beetles”. We lived way out in the desert a lot and learned how to survive and what native vegetation to eat, what could be used as medicine and how to fix it and soforth, and tonight my brother and I learned something new.

  23. I found a HUGE one of these Palo Verde bugs on its back and right smack in front of our front door here in South Scottsdale, AZ just this morning! Scared me at first. Then got hubby out of bed, and 2-3 times he took it further away (tried grass, rocks, etc) and she ended up right back at our front door upside now and legs going like crazy! She can’t seem to stay on her legs. Felt sorry for the poor thing, so we put her on some potting soil inside a box with a lid and holes. What should we do with her??? We think she may have laid a couple of eggs in the potting soil. Help!

    • You might try letting her go at night, after turning any porch lights off. They are often attracted to lights, so she might fly off in search of better lights elsewhere. Otherwise, not sure what to tell you! That’s not what I’d consider “normal” palo verde beetle behavior.

  24. We found two in our house, here in Tucson, in the last few days! And tonight we heard this weird hissing/scratching/munching sound coming from the floor board by our back door. Do you think the sound we heard tonight was just another one? Our backyard has about 4 wandering around right now…

  25. Thanks. One of these scared the crap out of my gf tonight and your Web page got us answers on what just landed flailing in front of us. Been in Phoenix for 2.5 years and haven’t seen one until today.

    • Though I don’t have any numbers to truly support this, people seem to see a lot fewer of the palo verde beetles in Phoenix than they do in Tucson, which may explain why you’ve never seen one! I wonder if the extra heat or the slightly different altitude or the relative lack of host trees or something is behind the difference, but there seems to be a big difference, in spite of the fairly close proximity. In any case, glad I could give you some answers!

    • If it’s in Romania, it’s not Derobrachus hovorei as it’s only found in the southwestern US. Your beetle looks like another beetle that’s fairly closely related (likely something else in the Prioninae subfamily), but the proportion of the antennae to the body aren’t right for D. hovorei and it’s in the wrong location. However, I’m unfamiliar with the insects in that part of the world, so I’m not sure what to recommend instead! Sorry I can’t be more help with the ID, but I do know that it’s not a palo verde beetle.

  26. This is my first summer to live in Tucson and I was totally caught off guard by these guys! I found one on my front porch, I ran in to get the camera and actually did get some decent shots. I am petrified of bugs that fly so I had really hoped the wings were more ornamental (shucks) They really are completely awesome as far as looking tough. A couple of nights ago I was dining at a restaurant outdoor patio and one came flying through. One friend said it was a humming bird and one said a bat, I told them I knew it had to be one of the same bug I found on the porch and sure enough I found your page and confirmed. It was really, NOT a cool feeling for it to be flying around during dinner, but they are awesome to look at while on the ground. I am thankful your bog is here and still educating newbies 3 years later. I posted a link to my fb and told all my Texas friends that I had found a winner over those dad-gum massive roaches they have.

    • Glad I could give you some useful information about one of my favorite beetles! I agree – having them flying around you is an interesting experience, but I’m glad you at least find them interesting on the ground. That’s more interest than a lot of people have in them!

      Hope you get to see many more cool things in Tucson! The Sonoran Desert is AMAZING!

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