Locust Borer and Nest of a Horsefly-Like Carpenter Bee

Subject: Maybe a Borer?
Location: Coryell County, Texas
October 1, 2013 6:28 pm
This visitor flew off within moments of landing, so I wasn’t able to get a really good photo, sorry. Is it a Borer, perhaps the Black Locust Borer? I looked this insect up on Bug Guide and your website, and I found the Locust Borer on your website from September 10, 2013.
According to notes I read, the male have longer antennae than the females, so this may be a male?
Its colors were alarming, and I didn’t actually want to get too close, although it’s probably harmless to humans, if not to trees. Its wasp mimicry worked on me!
Would this explain the buzzing-wing sounds and sawdust found near our oak firewood? We’ve tried to spot the buzzing-sound -and-sawdust-maker, but whatever it is, it’s a crafty insect and good at hiding.
Signature: Ellen

Locust Borer
Locust Borer

Hi Ellen,
While we don’t know what is buzzing and creating sawdust around the oak logs, you are correct that this is a Locust Borer,
Megacyllene robiniae, a species that appears in the autumn.  The adults are fond of goldenrod.  They are excellent mimics of stinging Yellowjackets and males do have longer antennae.

Update:  June 4, 2014
Subject: Horsefly-like Carpenter Bee Leaves Us in the (Saw)dust
Location: Coryell County, Texas
June 4, 2014 12:44 pm
Hello again. I realize that I should be working and will have to make up this time later this evening, ha!, but I remembered that I had written about the buzzing from the woodpile and sawdust before. I found that post: Locust Borer On October 2, 2013 · Category: Longhorn Beetles
The locust borer was not the insect creating sawdust, so I went back to the oak firewood just now and sure enough, more sawdust. I turned the log above the sawdust over, and found our Carpenter Bee, hard at work. The log has several tunnels carved into it by the industrious bees. I’ll attach some photos. In one, you can see her (?) abdomen as she busily kicks out sawdust. She paid absolutely no attention to me whatsoever. Another photo shows the entire piece of wood, and one shows the empty tunnel entrance after she had kicked out sawdust and climbed all the way back into the tunnel to chew some more. I wonder if the long tunnel to the right of the working bee had housed larvae before? It had some sort of substance in part of it, that looked like old sawdust, perhaps, or pollen?
I also discovered and photographed a beautiful little moth that was trying hard to look like a lichen, and succeeding very well. It can be seen at the lower left part of the log.
After taking the photos, I turned the wood back over and placed it where it had been before.
So, now I suppose we should locate the woodpile farther away from the house, given the bees’ prodigious wood-chewing abilities, and I’ll see about repainting the trim on the house soon to discourage any house-chewing, and I wonder if I’ll need to check for tunnels in the wood before burning firewood next winter? Would hate to be a home wrecker!
Thanks again! Love your site, except for folks’ parasite questions but that’s part of life, too, I guess.
How you answer so diplomatically I’ll never know, but I always learn something or have a bit of a laugh when I visit What’s That Bug.
Best wishes,
Signature: Ellen

Horsefly-Like Carpenter Bee
Nest of a Horsefly-Like Carpenter Bee

Hi Ellen,
We are so happy you wrote in after solving the mystery.


Leave a Comment