The ArthroBlogger
Fun stories. Random facts. All the arthropods.
Mud Daubers, or Spider Serial Killers?
I don’t think I’ve ever been to a park where I couldn’t look up in the corner of a picnic shelter and see a splattering of mud dauber nests. If I ever had to eat lunch under one such shelter as a kid, I would spend the entire meal watching those nests, always believing they were seconds away from spewing a horde of angry wasps at me. A number of knowledgeable adults told me I was safe and that mud daubers don’t like to sting, but it would be years before I realized they were right.
On a side note: I definitely didn’t think that the name was spelled “mud dobber” until today. Of course not, I’m a professional. Definitely not a second-year biology student googling arthropods in my spare time.
Mud daubers are actually pretty friendly, and by that I mean they won’t hunt you down and sting you senseless just for looking at them funny the way most wasps seem to do. Mud daubers can sting, but they aren’t very territorial and will really only fight back if you catch them and handle them roughly, or if you chase them and try to smack them with a spatula or something.
One of the reasons mud daubers are so nonchalant towards people is that, like the carpenter bees I mentioned in an early post, mud daubers are introverts who would rather live on their own than partake in the hustle and bustle of hive life.
Just because they don’t have building partners doesn’t mean that mud daubers aren’t good architects, though. These solitary wasps will scout out areas with plentiful building supplies (aka mud, preferably the clay kind) before getting to work to make sure they’ll have enough materials to finish the job. Once it’s found a good location, the wasp will roll mud with its mandibles like it’s making a snowball, then carry its “mudball” to wherever it wants to put its nest. It will continue collecting mudballs and spreading them together until the mud forms a tube, and voilà! House complete. While male mud daubers live in a single tube, mud dauber moms must create multiple tubes to house their young in, and that’s where things start to get interesting:
Although mud daubers aren’t a big threat to people, they probably frequent the nightmares of spiders. Once a mud dauber has finished building nurseries for her eggs, she goes out in search of orb weavers (a kind of spider I will be discussing in a later blog) and paralyzes them with her stinger. She will pack each nursery with living spiders before sealing them shut with her eggs inside. The spiders are still unable to move, and are trapped in the nursery until the eggs hatch and the baby mud daubers eat them.
Yikes. I was starting to like mud daubers for the whole reluctant-to-sting-people thing, but now they seem kind of sinister. There’s an orb weaver I named Charles who lives outside my window at home; maybe I should give him a warning. Or at least a tiny sword or something to fight off the mud daubers with.
To redeem mud daubers a little bit, I must say they’re pretty good parents. Butterflies just lay their eggs on a leaf and are like, “see ya! Good luck fending for yourselves, kids,” but mud daubers construct mud walls around their children’s nurseries and, while it may be cruel to the spiders, you can’t say they aren’t feeding their children well. Plus, both parents work together to care for their offspring: while the mom collects mud and puts the work into creating the nurseries, the dad will watch over the nest until it’s complete, protecting the exposed eggs from predators and parasites that wish to harm them.
This post has made mud daubers seem pretty busy and hardworking thus far, but not all species put in the same amount of effort. For example, blue mud daubers will use water (they carry it somehow, maybe in a tiny insect watering can?) to soften the mud of other mud daubers’ nurseries so they can break through and remove the eggs and spiders. Then, it’ll put it’s OWN eggs and spiders (why not just keep the old spiders…?) into the nest and seal it back up again. I guess mud daubers are jerks to spiders and other mud daubers alike. At least they still win the parent-of-the-year award – except for the fact that they leave once the nurseries are built and don’t stay around to ward off those blue cheaters.
Oh well. They tried. Next time they’ll install security cameras.
Blue mud daubers do have one thing going for them, however: they really cut down on your local black widow population. I guess we can’t complain about them wasting the other spiders if they’re going to be getting rid of these terrifying things. And hundreds at a time, too, depending on how many eggs they lay. I applaud you, you deadly-spider-killing-nest-parasites. Bravo.
The next time you see a mud dauber nest at your local park, don’t run aware in terror. Instead, thank these friendly wasps for leaving you in peace and eating hordes of deadly spiders.
And secretly pass out tiny swords to your neighborhood orb weavers. They’ll thank you for it later.
The ArthroBlogger 
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Oh my god I just disturbed a nest because I was worried it might be termites. It was nightmarishly horrific finding all those spider corpses in there. I legit had to jump around a while after to burn off the extra adrenaline.
On another note, glad to find another person who names their local spiders. All mine are called Dougie.
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