What are these cocoons? #733586 - Ask Extension


What are these cocoons? #733586

Asked November 09, 2020, 10:31 AM EST

When I remove my window screens to wash, I find these cocoon-looking things in the sides. It appears that whatever creature is building these cushions them with a nest. How do I prevent them from doing this? Is there something I can spray to keep them from coming back?

Ingham County Michigan

Expert Response


This looks like  nests of the grass-carrying wasp, a beneficial pollinator. You may be able to encourage them to build elsewhere by providing an insect ‘nest box’ of the correct diameter(8 mm) as described here-



You could also cut styrofoam, screen,  or cardboard covers for the track and insert them, when the tracks aren’t used for holding the frame.

More info here- https://extension.psu.edu/grass-carrying-wasp

Laura Sheffer Replied November 09, 2020, 11:47 AM EST
Excellent response, thank you! 
The Question Asker Replied November 09, 2020, 2:39 PM EST
You are welcome, glad to help.
Laura Sheffer Replied November 09, 2020, 2:46 PM EST

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