Blue Mud Dauber Wasps

2014 June 7

I’ve been meaning to post better pictures of the Blue Mud Dauber Wasp, Chalybion californicum for years, ever since I posted these pretty lousy pictures way back in 2009. So, in July of 2013 I caught not one, but two wasps to photograph. The first on was found dead on a windowsill on July 5;

and the second was caught alive in the back yard on July 12, when it came sniffing around the girls’ wading pool[1] (most likely looking for water to moisten the mud in her nest);

They do both appear to be the same species. In any case, there are only a few species of metallic-blue wasps with elongated waists like this, and Chalybion californicum is the one most commonly found near houses and structures.

There is another species of blue wasp that could potentially be found around here (the Steel Blue Cricket Hunter, Chlorion aerarium), but the Blue Mud Dauber has a fuzzier thorax, like this:

Also, unlike some other species of metallic-blue wasps, these have practically opaque wings.

They aren’t particularly agressive stingers, at least the live one didn’t offer to sting me even though I was handling her quite a bit. Their stings are mainly used for paralyzing spiders that they use to stock their nests. The adults don’t appear to eat the spiders themselves, they only feed them to their young. The adults evidently only eat things like flower nectar and pollen, and as a result their mandibles aren’t very aggressive (although they do look like they might be useful for carrying things like stunned spiders).

These are solitary wasps, although it is common to see lots of them all congregating at good nesting sites. They apparently prefer to re-use the mud nests built by other mud daubers in previous years, although I think they are willing to build their own nests from scratch if nothing better is available. When I was a kid, we had lots of these nesting in our outbuildings (mostly under the eaves, where it is dry), and since I don’t recall ever seeing any of the other common mud dauber species at the time, I expect that they pretty much had to be building the nests themselves.

While they use mud for their nests, they don’t actually need an obvious muddy area to get it from. They just need access to water, and some dirt. They are perfectly capable of rounding up the dirt from between blades of grass to make their mud.

[1] The problem with a wading pool around here is that if we freshly fill it with well water, the water comes out at about 45 degrees F, which is too cold to wade in. And if it is left full of water so that it is reasonably warm, it turns into more of a little pond, with all sorts of things living in it. We’ve actually gotten more in the habit of using it as an outdoor aquarium in the summer, than as an actual wading pool. We’ve successfully raised a lot of tadpoles to froghood in it, and little fish that we catch in the swampy pond in the woods do really well in it.

8 Responses
  1. June 7, 2014

    Are the eyes faceted? If so, the scale of the facets is so small that the eyes look smooth.

  2. Carole permalink
    June 7, 2014

    The black and yellow mud daubers around my house have been building nests. I thought the potter wasps were trying to steal the mud daubers provisions, but finally realized they were taking the freshly spread mud for their own nests.

  3. June 9, 2014

    KT: Yep, they have compound eyes with very tiny facets. This page has a map showing the distribution of facet sizes for a wasp’s right eye, and according to the figure legend the smallest facets are only 12 microns across, with the biggest ones being just shy of 30 microns. For comparison, 25 microns is the size of particles in a powder where it stops feeling “gritty”, so about the size of grains of cake flour or corn starch.

    I can probably get pictures of wasp or bee eye facets, but I’ll probably need to mount the camera back on the old microscope stand to keep it steady enough at that magnification.

  4. K T Cat permalink
    June 11, 2014

    Thanks for the link. It kind of got to the point, but it spent so much time talking about the evolutionary aspects of the eyes. OK, I get it already! The eye is superior to other designs! Sheesh.

    Here’s something I thought was way cool – images seen through a simulated bee eye.

  5. June 18, 2014

    After thinking about it, I wanted to extend and revise my remarks. I find the evolutionary biology stuff to be so obvious as to be unnecessary. “Because it flies faster and carries a machine gun, the Dorcus malorkus was able to out-compete the slower and totally unarmed Dasypus novemcinctus.”

    No, really? The evolutionary advantages they point out always seem painfully self-evident. What I want to see are the mechanics behind the tools. So the thing has a zillion eyes and the facets are tiny, what does that mean for the biological CPUs behind the things?

  6. June 23, 2014

    KT: OK. The main reason I linked to that article was just for the “map” of the eye, not for the evolutionary discussion (it was the first article I found that actually said what the sizes of the individual facets were). There are definitely better discussions of the actual optics and neural processing in insect eyes.

  7. Grant permalink
    July 12, 2014

    I just saw one of the potter wasps or a similar looking species enter the newly made chamber of the mud dauber nest by my front door. It was stealing spiders!

  8. Lisa permalink
    August 6, 2020

    Thanks so much for both articles! I’ve been wanting to know more about these beauties I hang out with daily. I have 2 nests under my outdoor table, and dozens of others around the house. One of them tried to bring a grasshopper in, but eventually gave up and the ants took it away. I’ve always called them my blue bees, lol. They often get inside the house, and will let me take them back outside. The reason I started searching for these guys is because I have one that is 5 times the size of the others. I thought it was a hummingbird at first.

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