Palo Verde Beetle is Ugly But Harmless

Do most grown men shriek like school girls at the sight of mammoth cockroach-like insects?

I’m asking for a friend.

I walked over to turn on the pool pump in its enclosure yesterday morning and jumped halfway across the patio. The fella in the photo above was perched on a rock and wasn’t moving. So I ran inside to Google “large black beetle Arizona.”

After a little internet sleuthing and increased confidence, I returned to the scene and snapped the photo above. (I really just needed some click-bait from the desert for my friends back in the Midwest).

About the Palo Verde Beetle

Derobrachus geminatus, or palo verde beetle, is native to the American Southwest and northern Mexico. This longhorn winged beetle is commonly seen here around Phoenix in the mid-summer when they take to the air. Well, kind of. These beetles are awkward fliers and have a zig-zag flight pattern due to their hefty weight-to-wing ratio.

Activity for this insect is mostly nocturnal and they are drawn to light. You might encounter one hurtling toward your porch light on a warm summer evening.

The fully grown adult palo verde beetle is about 3-5 inches long, is shiny black, and has a thorax (neck) with black spikes. Its wings are a coffee-brown color. Bulky, curved, segmented antennae protrude forward in front of the beetle. Six legs propel this desert dweller over brush in search of a mate.

The palo verde beetle (also palo verde root borer) is one of the largest beetles in North America.

Life Cycle

They begin life as grubs in the soil. The larvae then target the roots of dead and decaying palo verde trees, citrus trees and cottonwoods for nourishment. The larval stage can last up to three years. Later, large quarter-sized holes in the soil near the roots of a tree during the monsoons give a visual indication of the beetle’s emergence.

They surface in the wet, early monsoon season to mate over a 30-day period. The monsoon season is mid-June through late September here in the Valley. I made the acquaintance of the bloke pictured above on July 12th in my neighborhood near the Phoenix Mountains Preserve. June and July are prime-time for the palo verde beetle sightings.

Death comes to the beetle soon after the mating ritual. They don’t eat as adults, relying instead on the nutrition that was stored up during their larval stage. Its mandibles are used to subdue the female in the mating ritual. I have read accounts where the female even lost a leg and antennae in the fracas.

Summary

If forced to defend itself, it may pinch with its mandibles, but the black palo verde beetle is otherwise harmless to humans. No stingers, bite or venom. Just creepy-crawly desert awesomeness.

It is the palo verde trees in your Arizona backyard that stand to lose an encounter with this beetle. In order to discourage the palo verde beetle from choosing your yard’s landscaping as a home, keep your palo verde trees adequately watered, healthy and cut away any dead wood.

When I was ten years old, I saw a big, fat beetle get squished. I don’t recall the circumstances, but that’s not important. It’s the result that stuck with me. The beetle’s thick, viscous insides so closely resembled a crushed blueberry that, to this day, I can’t eat raw blueberries without feeling nauseous. – Jeremy Robinson, American author of science fiction novels