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I have found this little formation of ca. 5 cm (2 inches) near my bedroom window. I have seen no insects crawling or flying around it. I'm in southern Europe (Italy / coastal Tuscany), and it is late Spring.

Is this an insect nest? Maybe wasps? Is it something that I should be wary of, or can I just try and knock it down by myself (with some precautions, by night and after spraying it down abundantly)?

enter image description here

Federico Poloni
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2 Answers2

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Where I am here we call them mud daubers. They are a wasp which builds it's nest by forming wet dirt (mud). They are also called Mud Wasps. They are not terribly aggressive. Usually I just knock off the nest when I see them on my home. Cleaning off where they attach themselves can be a chore- usually it leaves a stain I cannot get off.

Kyle
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  • Usually the wasps will all return home from work in the evening. I tend to hose it down with wasp killer spray in the evening and give it a day or so to kill them, then knock down the nest. Fortunately, ours have all been outside, so I haven't worried much about staining. – FreeMan May 23 '22 at 11:12
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    @FreeMan They also tend to go relatively dormant when it gets cold out, so that's the safest time to mess with them. They'll probably be more aggressive during mid-day heat. – Darrel Hoffman May 23 '22 at 15:59
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    True, they aren't aggressive, but the sting is about 5x more potent than a yellow jacket. Also, they aren't a colony wasp. That is a single female's nest. –  May 24 '22 at 02:21
  • Thanks! I have broken down the nest with a pole (I couldn't knock it off intact in one piece). It was completely empty, no insects. I confirm the stain does not want to come off. – Federico Poloni May 24 '22 at 16:40
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This is a mud dauber nest. It is built by a wasp in the family Sphecidae, though other mud daubers with different shaped nests can be from some other families. Each cell of the nest is filled with spiders that are paralyzed. The female wasp lays one egg in the cell and the larva eats the spiders. The female flies to a pond or other water source where the bank has clay. She gathers a ball of clay and flies back to the nest. She works the clay in her jaws and adds it to the nest. She flies back and forth until the cell is finished. Then starts on a new cell. Stings are uncommon, but possible.

Timothy A Ebert
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