Blue Mud Dauber Wasp
When I was a kid, I used to find these blobs of mud stuck on our farm buildings, mostly under the eaves or in other spots where they would be protected from the rain. When I broke them open from time to time, they were either filled with paralyzed spiders, or had a wasp pupa inside. I’d often watch them being built and stocked by wasps that looked like this:
This is another old picture that I took in 2007, and the wasp was large enough that I tried getting the pictures without the macro lens, which is why the pictures came out a bit blurry. I also refrigerated it, which made it pretty much act as if it were dead until it warmed up again. This seems to be a trait of hymenoptera – ants, bees, wasps, and sawflies don’t seem to take cold temperatures very well.
Anyway, it is a Blue Mud Dauber, genus Chalybion. The metallic blue color is quite striking, and the elongated, very thin waist is very distinctive.
While they are wasps, and they can sting, they are solitary wasps and don’t generally sting people except in extreme self-defense[1]. They mainly save the stinging for the spiders that they catch to feed to their grubs. What they do is this: first, they build a tube out of mud. Then, they go and find spiders that they ambush, and quickly sting just so. They don’t kill the spider outright, because then it will start to rot right away. Instead, they just paralyze it, which keeps it fresh[5]. Depending on how big the spiders are, she’ll nab five or six of them and stuff them into the mud tube. Then she’ll lay an egg on them, cap the tube off with more mud, and start stocking the next tube. The egg then hatches, and the grub eats the paralyzed spiders as it grows. Then, come around fall, it pupates and waits for spring, at which time it finishes, pops out of the nest, and flies off to do in some more spiders. It’s a lot of work for them to build the mud nests, so frequently they’ll just clean out a nest and start over, or take over the abandoned nests of other kinds of mud daubers, or sometimes just take advantage of tubular openings that they find[2].
Whether these wasps are good or bad to have around kind of depends on your opinion of spiders. I’ve read that they will actually prey on black widows, if that’s the sort of thing that concerns you. Around here, though, the spiders they eat are really the sorts of things I’d rather keep around. Their mud nests are kind of ugly, too, and make things awkward when you need to repaint buildings.
I’m not quite sure why they specialize in spiders, it seems like it would be safer to go after things like caterpillars. The only reason I can think of, is that spiders are much less likely to have chemical defenses and toxins than caterpillars do[3]. It may also be that spiders are easier to paralyze for some reason, maybe it’s easier to hit their master nerve ganglion.
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[1] Most solitary wasps are pretty mellow that way, because there’s no percentage for them in stinging you unless you are actually killing them. See, if you have a whole nest of social wasps, then it is worth their while to sent a few out to discourage large mammals like us, because even if the defenders get swatted and killed, they are still likely to save the nest from being molested. The survivors can then continue taking care of the grubs, and the colony goes on. A solitary wasp doesn’t have that luxury, though. If she stings you to try to drive you away from the nest, and gets herself killed, then there’s nobody to stock the nest and the whole thing is a loss. It’s actually better for her to abandon a threatened nest and save herself, than to try to defend it. But, if you grab the wasp and try to kill her, she no longer has anything to lose, and that’s when she’ll sting you.
[2] My grandmother had these wind chimes that had kind of lost their chime, they just went “clunk, clunk” when the wind blew instead of ringing. I noticed that the weren’t working, looked into the tubes, and found that I couldn’t actually see through them. So, I took a piece of wire and rammed it through – and found out that the tubes were packed with mud. It seems they were just the right diameter to appeal to the mud daubers, and they’d used them for nests.
[3] Although, there’s one thing about spiders that live next to rivers and lakes. If the spider mainly eats insects that have aquatic larvae, those larvae are likely to have accumulated mercury from the water – particularly if they were predatory larvae preying on other, smaller animals. So, spiders in those conditions can have a very heavy mercury load[4]. This is evidently a problem for birds that eat spiders, because then they have an even larger mercury load, to the point where it can kill them.
[4] What happens with mercury is this: you start with a very tiny quantity in the atmosphere, that eventually gets caught in the rain and carried into rivers and lakes. The mercury then converts to a form that living things will take up. Plants grow, and some of this mercury gets into their tissues. An animal then eats the plants, and the mercury gets into their fat, which holds onto it. So, they end up retaining pretty much all the mercury that they eat, concentrating it to a higher level than it was at in the plants. Then something else eats the first animal, and concentrates the mercury still more. So, if you have a chain that goes something like algae => water flea => carnivorous caddisfly => bluegill => bass => you, there are four stages of mercury concentration before you get it. If we assume that each stage of concentration increases the mercury levels by a factor of ten, then you are looking at 10×10x10×10 = 10,000 times more mercury than if you had just eaten the algae. If, on the other hand, you have algae => carp => you, there’s only one stage of concentration, so you only get 10 times more mercury than the algae, which is much better. Basically, if you want to minimize mercury in your diet, you want to eat terrestrial plants, or animals that eat terrestrial plants, and you really want to avoid eating meat from carnivores that eat other carnivores that eat aquatic animals that eat aquatic plants. Eating meat from bears that have been eating salmon that have been eating other fish would be exactly the wrong thing to do.
[5] Which brings up one of my favorite entries in the Bulwer-Lytton Fiction Contest:
“Terry the Tarantula and Wendy the Wasp were frolicking and cavorting together in the Flowery Meadow, (as they were the best of friends in all the Enchanted Forest of Miggly-Wompsly) when, all of a sudden, and with no warning whatsoever, Wendy accidentally stabbed Terry with her stinger, making her very sad for she knew that soon her poison would paralyze her friend and after a while her eggs would hatch inside him, and then her happy wriggling larva would slowly eat him alive, but Terry tried to smile and would have told her not to be sad as this was how the Circle of Life was continued, but he was in too much pain and, as I mentioned before, paralyzed.” (Delano Lopez, Washington, DC, in the “Children’s Story” category, 2001)
Great post. Love the info.
Another wonderful post!
The short story brought a grin to my face, poor spider.
Thank you for these great pictures and the information. I have a question for you. We are seeing many (10-15) of these blue wasps visiting our grill. They duck into openings and come out. I cannot see mud nests yet. We have sprayed and antagonized the group of wasps, but they have not left nor died. Our concern is that we will heat up the grill and the wasps will not be happy and may want revenge! Why do you think we see so many blue mud daubers together? How can we get rid of them? Thanks for your post and any help would be greatly appreciated.
Kristi: I sometimes see large numbers of blue mud daubers hanging around particularly good nesting spots, so probably they are nesting in the grill. If there are crevices that they can use, they may be building the nests where you can’t see them. Spraying them may not do much, because if it is that prime of a nesting spot you might be getting new ones coming in to replace the ones that you kill off.
If you can’t plug the holes in the grill to keep them out, and sprays aren’t killing them, well, I don’t know. It kind of depends on what your grill looks like. It is possible that a couple of mothballs in the grill might make it unattractive to them. Or, if the whole grill gets good and hot when it is used, maybe you could just light it up, and then stand back while it burns until all the wasps are burned up. That *might* do it. Sorry not to be more help.
I have a whole swarm of them it seems hanging out around my soffit facia, under my eaves trough. One landed on my foot but didnt sting me. I’m wondering are these things attracted to sweet things like other bees and wasps? I am wondering because I would like to make a bee trap but my husband wasnt sure if they would be attracted to sweet. Thank you.
Wildly cool info! A definite indication that you are an intelligent being. I was wondering… I live in S.E. Texas and see these wasps on occasion, and we use the term “blue bottle” for them. Have you heard that term used for this wasp? Or is that term reserved for another species? Anyhow, I have also read that these wasps NEVER make nests; instead they recycle the nests from the other varieties of mud dauber. Anyway… great pictures, great info.
By the way… Today I had found a black and yellow mud dauber in my home. I captured him with a large plastic kitchen strainer and a book, and I was interested in identifying exactly what type of wasp this was. Glory to the internet. I found your site, and I am delighted to know that these wasps rarely sting. Currently it is extremely dry here in texas, so when I water the plants and the guineas I love to watch these wasps scrape up bits of mud. I have never seen construction in progress, but I will be seeking. Anyway, I let him/her free after a brief ten minutes of captivity, and I was interested in what they do when they are not busy building nests and laying eggs. What about mud-dauber sex? What do the males do? It is cool to see somebody with an “arthropod backyard exploration project”! ‘Round these parts, there is little to no intellectual activity. This site is very nice, and I will explore it more. Thanks for the information!
Jillian: I understand that the adult wasps mainly live on plant nectar (and to some extent body fluids from the spiders that they catch), so they probably are attracted to sweets. You may need to let it ferment a bit to develop a scent before they will be able to find it, though.
Robert: Around here, there is a species of fly that is about the same color, that people call “blue-bottle flies”. I’ve never heard anyone call the wasps that, but I’m sure that it varies by region. It’s not as if the common names are official in any way, in any case. As far as building their own nests, I think that they will if they have to, but that they will try to find an old nest to refurbish first. I’m not sure what the males do, I’m not sure I’ve ever seen one. Anyway, glad you like the site.
Thank you. I will let you know how it works.
We have a rather strange situation with a congregation of blue mud daubers each summer. Mostly before dusk, but sometimes in the afternoon, they fly into our porch area and roost together on the brick wall. This area is protected from the sun and wind. They sleep there at night and awaken in the morning to fly off. It is strange to see them mass together. I have counted anywhere from 10 to 20 of them grouped together. I cannot find any information of blue mud daubers roosting at night. Is this typical? I have a picture of this as well.
Well, it isn’t exactly the same species (although thread-waisted wasps are related to mud daubers), but Eric Eaton has a nice little article about sleeping solitary wasps. It’s evidently pretty common for solitary bees and wasps to sleep in groups like that.
A few years ago, I was stung on my hand by one of these blue wasps when I turned off the water faucet outside. I am not usually allergic to any bees or wasps, but when the blue wasp stung me, instantly my hand, then my forearm, and soon all the way up to my shoulder and neck were red, swollen and aching terribly. My heart started beating very rapidly, and I started getting dizzy. Have you ever heard of anything like this happening to anyone else? I’m not afariad of bees, but now when these guys come around I get the kids inside.
Nice bit of info. I have been wondering what type of wasp they were since they seem to appear every July here in Monroe County, MI at my house. I’m glad that they will not sting unless handled as I have no clue as to if I am allergic to bee/wasp stings or not; and I would prefer not to find out the hard way with me having asthma and all.
Kristi B.:
You had a anaphylatic reaction to the wasp venom. This can be life threatening. You need to see a doctor right away to get an Epi-pen in case of future stings. Sometimes, one is stung many years ago by a wasp or bee and nothing happens. This causes a sensitization in your body so that when you get stung again you have the reaction. This is what happened to me and I almost died. It must be treated as a medical emergency. Please don’t take any chances.