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Chalybion californicum- Mud Dauber Wasp

Chalybion californicum Metallic Blue Wasp, Mud dauber wasp
I was photographing some butterflies in my garden when this metallic blue wasp landed near me and startled me. The blue green color of this bug is striking and I'd never seen one like it in Chicago before. After some Googling I've learned that it is a Chalybion californicum or commonly called a Mud Dauber Wasp.

In all of the pages that talk about this particular wasp I couldn't find any information on whether it was beneficial in the garden or even a pollinator but I can't image it does any damage to plants. The one benefit I have been able to find on it is that it stocks the nest with black widow spiders after it lay eggs.

source: mud daubers


  1. Anonymous10:17 AM


  2. Hi,

    I haven't read anything about this wasp being toxic or anything of the sort. But of course if you are allergic to stings you should seek medical attention

  3. Anonymous2:03 PM

    Everything that I have read states that the blue mud wasp (chalybion) is not aggressive. I came across a nest under my patio porch and they were very aggressive! I was stung twice by the same wasp. Very painful burning sensation although it didn't last long. My daughter threw a rock up on the porch and five of them came out through a crack and attacked the rock, stinging it over and over...VERY aggressive. The pictures look exactly the same as the blue mud dauber shown on this site???

  4. Hi Anonymous,

    I've had a few of them make it into the house this year but they haven't exhibited any agression even after I've gone after them with the fly swatter. I'd contact someone to come and do something about the nest in your porch just in case.

  5. Interesting. I saw one here in Toronto for the first time this summer. Same thing: very blue-black colour with narrow waist. Research suggested it might be a mud dauber, but I was without camera when it flew by.

    Stocks the nest with black widows! Yikes! Its presence must mean a source of food nearby. Gotta stop leaving my garden gloves in the shed. Black widow spiders have started to infiltrate the Toronto area, so we'd best take care.

    Great photo. Is it yours?

  6. I had to add my comments on the aggressive nature of this wasp. For several years now, a few find a way into my house; I can't find how they're getting in. Many times, I am unaware that one is in my house until he stings me. The sting burns like the dickens. It doesn't swell very much like many other insect stings, but it itches terribly for days.
    Other than what I call a palmetto bug, I do not kill any creatures who come into my house. I put them outside. I am very frightened of the palmetto bugs although I don't believe they bite. They look like very large roaches and they can fly.
    When I have attempted to catch these mud daubers, they fly right at me and most of the time sting me before I can catch them. I no longer try to put them outside. Just the other day, I saw one at the window and tried to slap him with a magazine. He stung me between two of my fingers and then got me again on the inside of my upper arm. A couple of weeks ago, one got down the back of my shirt and stung me three times before I could stop him.
    By the way, I live in Southwest Georgia. I wonder if this is some sort of subspecies that is so much more aggressive than what so many others see.

  7. Anonymous12:03 AM

    I saw what I thought was a black stick on my carpet and I picked it up. Immediately it stung me and it burned like crazy! Because it hurt, I threw the bug when it stung me. The pain did not last long with in a few minutes the sting subsided. I had no idea if it was poisonous or not, or if I am allergic to it. So I decided I better find out. I found the bug and put it in a jar. I found pictures of a Chalybion californicum and it looks exactly the same the bug that I picked up and it bit me. But there is little information about the stings. Since there appears to be no swelling, streaking, or continued burning I am assuming it is not poisonous and all will be well. October 7, 2012



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