CLOSED: Leaf-shaped cocoons with worm-like bug inside

Tustin, CA

Hello,
Several of these leaf-shaped cocoons have appeared in my house bathroom. Some were in the shower and the one pictured was affixed quite high, approximately 5.5 ft from the floor, on a bathroom door. I am not sure how it got up there unnoticed. I nudged it and it began to move. A worm-like bug came out of the top end and began stretching out and moving the whole cocoon across the door, albeit very slowly. After a while, the worm went back into the cocoon, then emerged from the bottom of the cocoon and began exploring and moving again. The cocoons I found ranged from approximately 3/8 inch to about 5/8 inch in length and about 1/8 inch wide. The worm was very small, maybe 1mm in diameter.

What is this bug? Should I be concerned about a developing infestation?

I am located in Southern California.

Thanks.

Thumbnail by drex82 Thumbnail by drex82 Thumbnail by drex82
Minot, ND

These are household casebearers Phereoeca uterella (Lepidoptera: Tineidae), sometimes called ‘plaster bagworms.’ They are more of a nuisance than a true pest. See https://askentomologists.com/2018/07/22/the-household-casebearer-is-a-little-weird-its-also-one-of-the-most-common-pests-we-get-asked-about/ for more information.

Tustin, CA

Thank you sir!

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