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Photo#253801
Escarabajo - Xylocopa

Escarabajo - Xylocopa
Palo Alto, Santa Clara County, California, USA
February 15, 2009
Size: 2/3" long
This is a cross section of a 2x4, and some larvae can be seen in the holes. It's ~30 years old redwood, and was at about 4' above ground level. Is this unrelated to the Carabids in the other two photos? Thanks again!

Date
Date entered in "Date taken" field doesn't agree with date stamped on photo.

 
You are right. When I cut dow
You are right. When I cut down this rotten fence in '06 I first noticed the beetles, and thought mistakenly that they had made the holes. Now that I took photos of the beetles, and posted them, I found out through this wonderful community that the holes are totally unrelated to the beetles...

Holes in wood
These are not related to the carabids. Knowing the size of the holes would help, but the suspects for large (I'm assuming these are fairly large), round holes would be long-horned beetle larvae (Cerambycidae), horntail larvae (Siricidae), or nesting carpenter bees (Xylocopa). Whichever insects made these would be the size of the holes, so those little larvae are also unrelated.

 
Yes, the holes are large (~1/
Yes, the holes are large (~1/2" in diameter), but some are oval shaped rather than round, and they are like long burrows. I have never seen any other insects there. If there was a crust of leaves and mud for a long time, on top of this piece of wood, could the Carabids have made their home there at some point? do you know where do Carabid larvae grow?

 
Carabids
If this had been on the ground at some point, it's theoretically possible that some carabid (= ground beetle) larvae could have lived in it, but there is no reason to suspect that is the case. They definitely had nothing to do with making the holes.

Now that I think about it, given that it's redwood, carpenter bees are probably the most likely explanation. I suspect redwood doesn't have many species that eat its wood (i.e. cerambycids and horntails), but I could be wrong about that. I've never seen a concentration of carpenter bee holes quite that dense, but it could happen.

Please unlink, then.
Please unlink this image from the other two. Linked images are for multiple images of the same 'specimen' only. That said, I wonder if this is the work of carpenter bees (Xylocopa)? They tend to bore perfectly round holes in soft wood of structural timbers.

 
I unlinked it (I hope I did i
I unlinked it (I hope I did it right). I have never seen any bees there, and some of the holes have an oval cross-section. Also they go fairly deep, meandering in the wood, and do not have an opening to the outside, except through cracks (the openings in the photo are from when I cut the beam). In the garden we have wasps (they make nests in the eaves), regular bees, huge black bumblebees, and striped yellow jackets.

 
There you go! Those
huge black Bumble bees are Carpenter bees . All their holes are made to house eggs in chambers at the end, the female goes in and out repeatedly, so there is a round exit hole somewhere. But even if your holes are from longhorn beetle larvae - either you'd find them and their frass (eaten wood pulp) or there has to be an exit hole.

 
Thanks to everybody! The carp
Thanks to everybody! The carpenter bee picture settles it. Since they feed mainly on the rosemary and sage, when those start flowering I'll try to catch one to reconfirm the identification. In any event, my Carabs, now fully exonerated, can keep roaming and enjoying the yard :-)

 
LOL!
Well, I hope you let the pollinating carpenter bees off the hook, too!

 
Definitely! Now that I know h
Definitely! Now that I know how they look, I'll just check to make sure they are carpenter bees. I like them buzzing around the shrubs (overall I am in peace with aphids, snails, lizards, raccoons, ants, and whatever else comes to my yard).

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