What are these? I thought they were mud daubers, but I've never seen them in groups like this. They're in multiple places on my fence like this. No nest, they're just bunched up on the fence

The blue mud dauber (Chalybion californicum)

They group up, during different times of the year.

They aren't aggressive but can still sting. Normally when they are grouped up you get 5+ for 1 with a quick shot of wasp/hornet spray.

You just have not been on the end of a flying, stinging critter enough, I guess. I've been singled out of a crowd by Bees with attitude twice. I'll be the ne to get the Yellowjacket every time. Now I don't attack bees indiscriminately, but they do me.
I'd swear that built up pheromones in my body from stings attracts more even over time.

I've tried a couple times to get them w soap but there's no nest and they fly when I get close. Anything else I can try? They're eating my fence

Spray your fence with Bifen. I guarantee they stop eating it.

Thank you. I will mix some up now. Do I just spray where they're hanging out?

All over the fence

OnlyForNow said:

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All over the fence

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Hit the posts while you're at it. It's nice to punch a termite in the nose every now and then.

OnlyForNow said:

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All over the fence

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The whole yard if you want. Do it at dusk to not hit most of the good insects like pollinators but this kills the skeeters, beetles and a lot of other yard annoyances. The grackles had a field day the next morning eating all the dead bugs, musta had 20+ scouring my backyard for hours.

OnlyForNow said:

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All over the fence

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Will bifin I/T work? I have some on hand… or do I need the XT?

Yes. IT is lower concentration and water based, XTS is high concentration and oil based.

IT won't last as long.

Also,

paying closer attention. Those guys aren't eating your fence. They are mud daubers, and catch spiders for their young in the mud nests. Something else is chewing your fence up. By the looks of it, it was "infected" when purchased.

I'd 100% remove that board and replace it. It looks like it has other larvae in it making their way to the surface.

Why aren't these mud daubers building mud nests? They've been piled up right there on my fence for weeks

Also, fence had been up almost a yr… what kind of larvae would take a year to hatch

They congregate sometimes, for some unknown reason.

They did it/do it on the corner eve of my house and the basketball goal and net - about once a year, starting a few weeks ago.

It takes one good blast from the spectracide can and they don't come back.