Mason bees use a two foot long nesting tunnel.

Two feet long tunnel filled up to the 19 inch mark!
A long nesting tunnel  for a mason bee

 Hi Margriet, Well they have gone and done it again. You know that 8ft long escape box (emergence box or shelter), well I was cleaning it up for this season and noticed one of the escape runners looked plugged so I decided to take it apart to clean it. This is what I found. What do you think?  Dave  M. from Port Alberni, Vancouver Island, British Columbia.
I have not seen this before, but I am not surprised.  As in your photos (see recent blogs), mason bees will nest in any type of ‘cavity’ (umbrella for example)!  Thank you for sending the photos.  Margriet