What The Heck Is That Monstrosity?

I recently had a knee injury and was ordered to stay off it for a couple of weeks. During my forced vacation, I spent most of my time on the living room couch. From that vantage point, I could watch the dogs going about their business in the backyard. 

One evening I noticed that Bob, our large Shar-Pei/Lab mix, was acting strangely. He was dancing around, jumping and pawing at something on the ground. He looked exactly like a fox hunting for mice under the snow. You could almost see the thought bubbles over his head saying, “What the heck is that monstrosity?”.

Bob is generally a dignified and somber older gentleman and this behavior was decidedly unusual for him. So, ignoring the admonishments of my family to stay put, I hopped over to the door to see what had poor old Bob so upset. 


What I saw made me laugh – Bob had come across a particularly large Palo Verde Beetle. I have seen large humans freak out when they see these bugs, so it was perfectly acceptable to me that our dog would go bananas over it. As I stood there laughing, Bob took one more manly leap and crushed the beetle, then quickly ate it. What had been funny was suddenly just gross.

Palo Verde Beetle - Photo courtesy of Jen Ragan

I have lived in the Arizona desert for most of my adult life, so Palo Verde Beetles are nothing new to me. We are used to seeing them in summer months. However, after Bob ate the bug, I began to worry if they could harm dogs. That’s when I realized that, while I may have seen them before, I knew very little about these insects. A few Google searches later and I had discovered a number of interesting facts about these unique creatures:

• First of all, eating a Palo Verde Beetle won’t hurt a dog. In fact, their natural predators include a very close relative of dogs – coyotes. Other predators include bobcats, roadrunners and owls. Skunks, coatimundis and bears enjoy munching on the insect in its larval form.

• Commonly called the Palo Verde Beetle, its proper name is the Palo Verde Borer Beetle (Derobrachus geminatus). It is one of the largest beetles in North America. It has shiny brown-black in color and can easily grow to be 3-3½” in length. When you add the wings, large pincers, spiny collar and long antenna, it really is a monster-sized bug. Many people think it is a mutant cockroach when they first see it.

• Female Palo Verde Beetles lay their eggs in the soil near trees during monsoon season. When larvae hatch, they bore into and feed on the roots of the host tree/plant. They are partial to Mexican Palo Verde, citrus and olive trees, as well as rose bushes. Larvae stay in the roots for 2-4 years before maturing into adults. They then create small (about the size of a quarter) holes and exit through them. These adults live only about a month before mating and dying. 

• It is during their short and desperate search for mates that people and beetles cross paths. They are nocturnal (coming out in early evening) and are attracted to light. So, it is common for them to make appearances where you have outdoor lighting. You may see them at an evening barbecue or have one seemingly waiting in a light puddle by your backdoor. The favorite trees of the Palo Verde Beetle are also the most common, so if you live in the desert areas of Arizona, it is likely there are beetles around your home. We have several large olive trees in our backyard; they are probably where the poor ill-fated bug that Bob caught came from.

• Despite their fearsome appearance, Palo Verde Beetles are, for the most part, harmless to people. They are not poisonous and do not sting. Their large mandibles are used in fighting for the right to mate and in subduing females while mating (which can be quite violent). However, they may give you a nasty bite if you pick them up. It’s best to leave them alone.

• Palo Verde beetles have wings and can fly, but they are not graceful fliers. Instead, they propel themselves in an ungainly manner from place to place. While they are flying, they can be a real hazard to motorcyclists. If you have ever been hit in the face by an insect while riding, you know how painful it can be. Imagine getting hit by this monster!

• While it’s true that these beetles feed on roots, they don’t like new roots and choose only decomposing ones. They pose little or no threat to healthy trees and shrubs. Provide your vegetation with proper fertilizing and watering and you need not worry about the Palo Verde Borer. Otherwise, they can be difficult to control because you may not know the larvae are in your trees since all the larval activity is underground (2-4 feet below the surface). Exit holes can be seen around the base of infected trees, but by the time this happens, the insects have already left the tree. So putting insecticide in the hole is exactly the same as closing the barn door behind the cow.

• If you are determined to rid your area of these short-lived bugs, the following measures can be taken:
• Screening off patios and other outside areas where people gather
• Changing out exterior lights from white to yellow
• If you absolutely must kill them, try a pyrethrin based aerosol like Azera Gardening  or Monterey Fruit Tree Spray Plus.

Handsome Bob

I’d like to encourage everyone to enjoy the seasonal oddity that is the Palo Verde Beetle. He isn’t really a monster; he’s just another lonely being in search of love. Who is also, apparently, a delicious dog treat.

- Submitted by Pam from ARBICO Organics