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Blue Mud Dauber - Chalybion californicum - female

Blue Mud Dauber - Chalybion californicum - Female
Sunnyvale, Santa Clara County, California, USA
June 19, 2007
Size: approximately 18-20mm
Found patrolling my backyard pond. Polistes Diminulus present in same area in numbers. They may be avoiding the larger black wasp, I'm not sure.

Images of this individual: tag all
Large Black Wasp - Chalybion californicum Blue Mud Dauber - Chalybion californicum - female

I live these guys.
My mom constantly "accidentally" kills them all the time. If I find them in my room I just let them be. But if my mom sees one or I find one in another room I just lay my hand in its path until it crawls on me and take it outside. They're gentle little bugs. One of few I'm ok with. Also infant leaf legged bugs (orange with black spike like things) are chill lol.

Questions about this bug.
We have killed like maybe 6 of these wasps in my little girls bedroom window. If the is a nest near by the window, will they keep coming inside in window some how? (They just stayed at the windows.) What are they doing here in this state, Indiana, if they are from california? How do I make they don't come back or where they nest is, if they have one? PLEASE help, my little girl didn't want to sleep in her room because of them.

These are friends!
PLEASE don't kill these. I wish we had more where I live. They are quite beneficial, as are most wasps. These are, indeed, very timid and you would have to go way out of your way to be stung by them. If they are in your house, try to shue them to the door or gently capture them in a jar and set them outside. They kill more than black widow spiders, too. They prefer the Hobo spiders here, to place in their mud hut nests (1/2 inch dia X 2-4" long) for their hatch to eat in the spring. You can find their nests attached to under hangs of rocks, concrete and downed trees. You can approach their nests without fear, so get some pictures if you do. Look for them in mid summer in your gardens during and after watering. They are impressive looking in direct sunlight. - Thanks

Re: These are friends!
I have to agree. We used to have many of these that lived in our garage in south Texas. As children when we would go in there to work on our motorbikes (or later, when we were older, riding lawnmowers), they would always be flying around somewhere or other. They always go out of their way to avoid contact with you, and after over 15 years dealing with them I have never heard of them stinging anyone. They were extremely beneficial in that they really helped keeping the black widows away (in an unfinished garage, the black widows used to find PLENTY of places to set up shop). They used the abandoned nests of the yellow-brown dirt daubers wasps. None of those ever stung any of us either. While my father did go after the yellowjackets and red wasps (those are very, very mean), he always told us to leave the blue and yellow brown dirt daubers be.

You were lucky to have a dad like that!
Sharing his observations with you, and helping maintain the the awesome blue mud daubers and other beneficial wasps. As for yellowjackets...I know they are a part of nature and in some venues are even welcome. But their aggression can be too much.

One positive for the yellowjackets though. When I lived in a California location where biting stable flies were a problem because of their painful bloodsucking of dogs and humans, often I would swat a stable fly out of the air, and before it could recover, a yellowjacket would swoop down and grab it. Yes!

The only things that come to mind that might help...
...for one thing, if you remind her that these wasps are spider killers that might be somewhat comforting. Secondly, I had a hard time getting close enough to get photos! They seemed very timid!


The obvious ID would be the Blue Mud Dauber Chalybion californicum, which hunts spiders. Obvious, and quite possibly wrong.

There's another very similar-looking wasp, Chlorion aerareum, a cricket-hunter, that looks the same to the untrained eye. Best to wait for a trained eye to confirm which this is.

Blue Mud Daubers
By far my favorite-looking bug of them all. No other bug has such a striking metallic blue color. We had a few of them hanging around the house when I lived in Grand Junction, Colorado. But I did some digging and found out that they are a bad indicator of black widow spider infestation because that is their favorite food. Our house was, of course, full of black widows.

That is a very interesting addition!
We are definitely on the same wavelength, I think. For one thing, I still feel bad I didn't get any better photos of this insect because it really is a beauty.

The second thing you mentioned...Black Widows! I was a little unhappy about the fact that this house was a Mecca for Black Widows. I had the misfortune of being bitten in the elbow by one, and it was phenomenal how long it took for the swelling to go down (At least two weeks!). On the plus side, it did not seem to be all that painful. In the end though it has left me with a real aversion towards this type of spider!

ID help?
Hi.. I am much much better at ID'ing birds, and often the only way to determine once and for all a tricky ID is by behavior.
I'll confess I am no expert on wasp ID, but I noticed one thing from the main description that might help. it was stated that the wasp twitched it's wings alot. Don't mud daubers do that alot? Unless the cricket hunter does that too, the behavior might confirm your initial ID of the blue mud dauber.

If not, forget I wrote this. ;) just thought I'd chip in.


Thanks Karen!
I was thinking along the same lines, however, I was surprised to read someone also attribute the the clicking to a cricket killer, so my hopes were dashed! I still see this wasp often. Maybe someday I will see him with his prey!

A thought
I am researching common backyard wasps for a public educational program I'll present this September, and I remembered reading something Eric Eaton wrote in another posting series regarding these same two species. (Wow... how's that for a run-on sentence, eh???)
Anyway... HE said that Chlorion aerarium (Steel-blue Cricket Hunter) is "rarely seen at flowers." Keep an eye out and try to observe whether or not he/she visits your flowers.

I see you noted your pretty wasp patrolling your pond. Try to see if it gathers blobs of mud. If yes, it's the dauber. The Cricket Hunter is a digger, so they won't be interested your mud.

If you're not familiar with the Blue Dauber's nest, here's a nice shot:

Sooo.... twitchy wings, flowers, and mud nest= Blue Dauber.

I also have Daubers (Both Blue and Black and Yellow) that visit a muddy spot in my little pond, and they even have a pair of nests right on my porch- across from the Paper Wasp nest! I also have Great Golden Diggers, and Golden Diggers. Not to mention oodles of bumblebees. It's funny..I never really noticed them until I started to do this program's research. Now I see them everywhere. cool, eh?

Hope you'll enjoy your detective work! I love this sort of thing. if I can't figure out what something new is, it actually keeps me awake sometimes! I'll obsess over it until I get it! I'm wierd that way.
But hey... it's my job. How cool is that??????!!!!



I can relate-
In the past I may have gone to greater length to solve this mystery. The mitigating factors are that the entire insect world is like a new discovery for me. I think of it as a blue mud dauber, though, it is just tentative. There are far more spiders around here than crickets, so I just don't see why cricket killers would make a home here. It is a very rare night that you can hear a cricket. That and the fact that the size seems closer to that of blue mud dauber. In my patio, laundry room, there is a strange mud nest but it is small and just has one hole, like it housed only one insect. It is located high up on the wall, and has a very odd green color to the mud. The single hole is pretty large too. I don't think it is being used, but then, I have only looked during the day so who knows.

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