banded alder borer | wordsfromanneli

When I found this beetle sitting on the underside of our deck railing, I decided to catch him in a glass. Now what? Having captured him, I felt responsible for him.

Do I let him go? Is he a good bug or a bad one? What if he’s harmful to the trees, as I’d heard on the news just the other day? Do I have to kill this bug and save the forests of the world? I had heard about Asian longhorn beetles. Was this one of them?

But who put me in charge of the insect world? What conceit for me to assume I had the right to make a life and death decision for this insect.

I looked up information on this beetle and discovered that this was a banded alder borer (rosalia funebris) of the longhorn beetle family.

As adults, they eat flowers (well, I didn’t like to hear about that so much, but it was better than eating a tree), and the larvae of the beetle eat the decayed wood in which the eggs were laid. Not much of a threat at all.

The banded alder borer is not prolific here, and is not going to kill the trees around my house.

He had spent enough time as my prisoner. I lifted the paper cover from the glass. The beetle seemed eager to fly away, and yes, you guessed it. He flew right onto a flower bed I had planted this spring, where I’m sure he had a good lunch.

Many years ago I saw one of these beetles in my yard and later wondered if it was one of those terrible Asian longhorned beetles that destroy our forests. Should I have killed it and saved our forests?

Most likely our forests were not in danger, and I’m glad I didn’t kill the poor bug. Yes, it bores into wood and lays its eggs there so its progeny will also bore into the wood, but it prefers dead wood. By eating the dead wood, it is actually doing more good than harm.

Today, I found this poor little guy already dead on the walk beside my house. I picked it up with my bare hands in spite of the horror I have of touching bugs. If it had wiggled, I would have been in trouble. But no, it didn’t move. I wanted to take its picture so I could identify it for sure.

I apologized to it for placing it in such an undignified pose, but I wanted to be sure, in case I needed to confirm its I.D. by its underside. If you click to make the photo below bigger, you can see that it has fuzzy mitts on its front legs and tufts of “fur” on its antennae.

Here is what I found out.

It is a banded alder beetle, often confused with the Asian longhorn beetle, a
damaging exotic pest.

I found more information at this site:

https://entomology.oregonstate.edu/sites/agscid7/files/entomology/Banded_Alder%20Borer_13.pdf

They said:

The easiest way to distinguish these two species is to look at the segment directly behind the head. On the Asian longhorn beetle the area is entirely shiny black while on the BAB the area is white with a single, large black spot that occupies 60% or more of the segment.

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