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Entomology (Study of Bugs)/Is this a Mud Dauber nest?



I would love your professional opinion/advice.  I discovered this clay construct at the top of my doorway coming into my kitchen, which is the door I exit/enter from every day, between the main door and the screen door.  I just found it last night and I haven't observed any activity around it, but is it a Mud Dauber wasp's nest? Should I be afraid to remove it myself?  I live in Los Angeles, CA, by the way.  I have two small dogs and I don't want to risk their or my health.

Thank you so much for any light you can shed on this!!!  :)


ANSWER: Johnny:

Yes, it is a nest of the Black & Yellow Mud Dauber, Sceliphron caementarium .

What I would like to know is how the wasp got in between the two doors to make the nest in the first place.  If you did not notice it coming and going, why would there be a problem now, when it appears to be complete?

Next year, the wasp's offspring will be chewing their way out, but they should have no trouble escaping if their mother was able to get in to make the nest.

Mud daubers are solitary, and unless you physically grab one, you are not going to get stung.

I hope this puts your mind at ease.  Please do not remove the nest until the wasps have emerged next year (you will see holes where they have chewed their way out.  Allow about a week or so from the time you see the first exit hole).


---------- FOLLOW-UP ----------


Thank you so much for your response.  I don't want to harm the wasps, but the reason they got in is that the screen door hasn't been shutting properly lately, leaving a huge gap for all kinds of critters to get in.  I want to get this fixed, partly to keep critters out, but also to be able to have my main door open while having the screen door closed and secured, allowing airflow into the house without leaving the screen door ajar where my dogs can get out or other animals can get into the house.  (A bit ago I live-captured two mice that had snuck in somehow and I released them back into nature.)  So, if i secure the screen door, i don't think come next Spring the wasps will be able to exit to the outside...which is not a good result for either them or myself.  Is there anyway to move the nest to an outdoor location without destroying it or the wasps?  Leaving my door ajar until Spring really isn't that great an option.  ;-)

Thanks again!

I see now....

You could try gently scraping the whole thing off with a putty kife, then carefully gluing the nest to the underside of a board leaned against the back fence or something.

Scraping the nest off could well expose the contents of at least some of the cells, and the larvae or cocoons need to be insulated, which is why I suggest gluing that side of the nest to another durable surface.  I'd use a glue that has no fumes, like Elmer's or something.  I know, a lot of fuss, but you did ask. :-)

Thanks for your concern for the wasps.  It is a common species, so probably no harm whatever you decide to do.


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Eric R. Eaton


I answer insect and spider identification questions ONLY. Attach images if possible. No "what bit me?", "what do I feed this bug in captivity?", or science fair project questions please. NO TECHNICAL QUESTIONS ABOUT INSECT PHYSIOLOGY.


Principal author, Kaufman Field Guide to Insects of North America. Professional entomologist employed previously at University of Massachusetts, Chase Studio, Inc., and Cincinnati Zoo; contract work for West Virginia Department of Natural Resources, Smithsonian Institution, and Portland (Oregon) State University.

Author, Kaufman Field Guide to Insects of North America, Missouri Conservationist magazine, Ranger Rick, Birds & Blooms, Timeline (journal of the Ohio Historical Society). I have contributed to several books as well.

Oregon State University, undergraduate major in entomology, did not receive degree.

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Principal author of the Kaufman Field Guide to Insects of North America, Smithsonian Institution (contract), Cincinnati Zoo (employer), Portland State University (contract), Chase Studio, Inc (employer), Arkansas Museum of Discovery (guest speaker). Currently seeking speaking engagements, leadership roles at nature festivals, workshops, and ecotours.

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