At first I thought these were the paper wasps as they held their wings outspread but the image below of those wasps from the Polistinae family shows a completely different body pattern. Dr. Matthias Buck of the Royal Edmonton Museum is working on samples of these to do DNA sequencing.
The photo above is of one of the better colonized box of tubes from the summer of 2015. Each mud-sealed tube in this box will contain on average 5 mason bee cocoons.
In the lower section of the box shown below, several mud plugs are of lighter colour and a smoother texture. I have found that these ones are colonized completely by another bee, I thought they may probably be resin bees , but now I have found out they are from the Subfamily Eumeninae (Potter and Mason Wasps):