This time of year I have pollinators at my bee blocks looking for spaces. I drilled 1/8”, 3/16”, and 1/4” holes in some blocks of ash that a friend gave me. They seem to prefer the 3/16” but all three sizes are filling. I don’t know what these are, bees or wasps? Some of the capped holes have green tinge to them making me think they are leafcutter bees. Some of the caps have purple tinge, maybe from berry juice?
Those are bees and not wasps. They do have the appearance of the leaf-cutting bees.
Leaf-cutting bee blocks are a thing. A web search may reveal a preferred hole size.
Perhaps the purplish cells are from purple foliage. Look around your property to see
if there are any leaves with missing arc-shaped pieces.
After I posted the photos I discovered some spaces in my mason bee blocks were capped with leaves so I think the original photos were some sort of sweat bee and not leaf cutter bees. Today I found a yellow twig dogwood with lots of circles cut out.