Cocoons in cotton-like material

From: Harriet W
Subject: weird yellow fluffy substance found

Message Body:
When I was recently taking down my mason bee hotels and houses, I found a yellow fluffy substance in several of the boxes.  It seems almost like wall insulation.  One seemed to have cocoons in it.

Do you know what this is?  Should I just clean the cacoons and boxes as usual with Chlorox? Do I just throw this stuff away?  leave it in the recycle?

 I have tried to take the pictures and enclose them here.  One is clearly in the well for the new cocoons, the other (with several pieces) comes from within one of the houses.  I am quite curious about what you think they are.  I also cannot determine whether they are beneficial to my bees, or not: ex. should I try to “clean” the ones that seem to have some solid masses within?
 
Many thanks for your time. 

Hi Harriet- Others have found this type of insect in their mason bee homes.  I usually place odd things like this in an emergence box, so I can re-examine it early next spring.  We are still not sure what it is.
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