Black and Yellow Mud Dauber

2009 March 21

I found this wasp crawling on our window at about the same time as we found last weeks Blue Mud Dauber (mid-July of 2007[1]). This is the related Black and Yellow Mud Dauber, Sceliphron caementarium.


Like the Blue Mud Dauber, these have a very long, thin waist. I’m not sure why that is, it must give some advantage. Maybe it gives them the ability to sting a spider without getting close enough to it to risk getting bitten?



They also build nests out of mud and stock them with spiders for their young, same as the blue mud daubers do. In fact, they arguably do it better than the blue mud daubers do. The black and yellow mud daubers evidently prefer to start a fresh nest from scratch every time, like this one that we found under construction in our barbecue grill. Meanwhile, the blue mud daubers frequently take over and refurbish the nests that the black and yellows emerged from (and then abandoned).


The tendency of mud daubers to fill tubes with mud and spiders is not necessarily innocuous: they have a tendency to plug the pitot tubes[2] that make up a critical part of the airspeed indicators in airplanes. There is at least one serious plane crash that was probably caused by mud daubers.

Aside from color, and the few differences in their habits, the black and yellow mud daubers and the blue mud daubers are basically in the same ecological niche, and I imagine that they compete directly with each other. So, most of the things I wrote about the blue mud dauber also apply here.

[1] Again, these wasps were big enough that the photographs were taken without the macro lens, so they don’t show as much fine detail as I might like. The surface it’s laying on is a standard playing card (the eight of hearts from a standard “Bicycle” deck) if you want a sense of scale. Anyway, the snow is finally melting, and within the next couple of weeks I should be able to start taking new pictures again instead of having to haul out all these old ones. So, hopefully the picture quality is going to improve.

[2] A pitot tube is a tube pointing in the direction that the plane is flying, so that air rams down its length and develops a pressure. The airspeed indicator works by comparing this pressure to the pressure in an outlet that does not have air being rammed down it, and calculates the airspeed from this pressure difference. Obviously, if the tube is plugged up by mud, it isn’t going to work right.

21 Responses
  1. March 22, 2009

    I feel your pain about posting old less-quality-than-you’d-accept-today archive photos. I’ve been doing that for months… Stupid snow.

    But the photos are actually very good, and more than enough for identification purposes.

  2. March 22, 2009

    I imagine their central nervous system is much like spiders’ – a bundle of nerves mashed together near their heads. Your earlier post on the digestive system of a gnat gives me greater appreciation for these insects’ dining habits. You can look at these guys and imagine the cutaway view …

  3. March 23, 2009


  4. March 23, 2009

    Yes, we still have about 1 to 2 feet of snow on the ground here. It’s in the process of melting, but it probably won’t be all gone until around the end of April.

  5. March 29, 2009

    What’s in that narrow tube that connects the body to the tail end of the beast? It looks like it’s just a pipe. Does the tail end have intestines?

  6. April 3, 2009

    Oh my we have those here too sometimes, I usually run away from them, lol. Anna 🙂

  7. April 13, 2009

    As far as I know, yes, the digestive tract has to run through that narrow waist, as do the circulatory fluids (if they are like other wasps and bees, the kidney equivalent has to be in the abdomen, so hemolymph from the rest of the body has to get into the abdomen and back, somehow). The adult mud daubers evidently have a mostly liquid diet (they go after plant nectar and the like for themselves, the spiders are only for the grubs to eat), so that probably helps in moving things through that long waist.

  8. debbie permalink
    July 4, 2009

    I just caught a live Yellow and black mu dauber, i was wondering how do you kill a whole nest of them, they are making a nest in my outdoor patio light fixture, they enter by where the screws go and leave via the over hang?

  9. April permalink
    June 19, 2010

    These mud daubers are actually a solitary species… meaning there isn’t a “whole nest” of adults. So, you can just knock down the nests & hose them away to get rid of them. That way, the blue mud daubers won’t come looking to use the old nests. The nests are filled with paralyzed/preserved spiders, and mud dauber larvae/cocoon/etc. so spraying them with a hose, or smashing them should work, I imagine. These are non-aggressive wasps, though, and really quite fascinating… you don’t *have* to kill them 😉

  10. Katie permalink
    June 20, 2010

    I actually think that the blue mud daubers are less intimidating and scary than the yellow and black wasps. I actually am very scared of any type of bee, wasp, ect…. so I just run away and hope that they wont follow me! 🙂

  11. Roberto Granados permalink
    April 28, 2011

    We’ve got those here,too.Twice we got one in the house,which freaked out my Mom.I think they are interesting,though.

  12. Lori permalink
    May 25, 2011

    I have found 6 to 8 in my kitchen/dining room in the last 18 months. I find it hard to believe they are coming in from outside as we are so very careful about closing doors up quickly and I don’t see any nests that may be close to doors. Is there a chance they are making a nest in our attic/ceiling and then getting into the rooms through the recessed lighting? HELP!

    (I’m seeing the black & yellow version)

  13. May 26, 2011

    Lori: It is indeed quite possible that they are nesting in your attic and then coming in through the light fixtures. Mud daubers really like nesting in attics, if you go up there you will probably find dozens of nests. And, most houses aren’t sealed nearly as well as one might like to think. Light and electrical fixtures, poorly-seated weatherstripping, and even gaps around windows are practically a highway for insects to get into the average house.

    If you can get into your attic, you’ll mostly find the nests built up in the underside of the roof. Like most wasps, mud daubers seem to like to raise their young where it is fairly hot.

    If they are in your attic, the most straightforward way to keep them out of your house is probably to seal the light fixtures. Electical box sealing tape should be available at any lumberyard or hardware store, we have it in all of our electrical fixtures.

    Of course, since they are not likely to sting unless molested, the easiest solution is just not to molest them. Maybe just open a window and shoo them outside. Or, if they have to be destroyed, just cutting them in half with a long pair of scissors is surprisingly easy and effective.

  14. Claudia permalink
    August 13, 2011

    I have a black and yellow mud dauber nest outside my front door, and today was the first time I ever saw the wasps themselves after reading about them for a month. I read that they are a solitary species, however, there were two wasps working on the nest together! It is not two nests, I am sure, just one lump the size of a child’s fist. They are adding fresh patches of mud to the outside, and have plugged up a small hole about twice the size of this O that had appeared a few weeks ago. (The nest originated as a tube with the typical large hole in it, which was sealed up. Then it became a large ballish shape without us even noticing.) Do you know why there are two, and what they are going about doing with th nest?

  15. August 14, 2011

    Claudia: My understanding is that black-and-yellow mud daubers just keep building onto their nest until something happens to them, so they start with one tube that gradually gets bigger and bigger. As for the second wasp, I have never noticed mud daubers being particularly territorial, and many wasps will often nest in the same general location. It takes less mud to build a tube on top of the existing tubes than to start fresh, so it makes sense for multiple wasps to merge their nests together into one communal nest.

  16. Claudia permalink
    August 14, 2011

    Oh, thank you for your advice! Is this somethig I should be concerned about, two wasps growing into a nest of many more? They don’t bothere me at all, in fact, I find them quite endearing as they work so hard, but since this nest is right outside my front door, my parents really hate them. All i can do to save the nest (until the cold months, at least) is to tell them about all the good things about mud daubers. I don’t think a huge communal nest would likely help my case.

  17. August 15, 2011

    Claudia: I don’t think it is going to get any more communal. By this time of year, all the wasps should have established themselves in a particular location, and I wouldn’t expect more of them to come by looking for nesting spots at this point. They’ll probably finish up one way or another in a couple of weeks, and then you will just have a harmless blob of mud until spring.

  18. Claudia permalink
    August 15, 2011

    That sounds great. They really are fascinating to watch. Thanks for all the help!

  19. Lori permalink
    August 15, 2011

    Just getting back to this. Are attic isn’t accessible (flat roof). It’s an old house and I dont feel like paying someone to seal up things. They don’t bother me or the kids so they are fine where they are.

  20. Josh permalink
    July 17, 2014

    OMG!! I just saw one in my back yard. scared the crap out of me!!

  21. October 29, 2018

    Seen quite a few here in South Africa. Probably one of the least aggressive wasps I have ever seen, plus they catch all the spiders around the house. Been trying to figure out what thy are called for an wile now, so thanks

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