Some time ago I created this pile of rubbish with a view to attracting some small sized wildlife. I did not think it would be very successful, however, to my surprise a leaf cutter bee has laid some eggs in there.
They are solitary bees and cut circular holes in the leaves of trees and shrubs and use them curled up to make cells for their eggs. If you look closely at the ends of the canes you will see that some of them are sealed with pieces of green leaf. They also made all the mess at the bottom of the pile of canes. I assume it is the material they cleared out of the canes.
This is where the circles of leaf came from - a cornus I had rooted and which was located in a pot close to my bug home. The bees lay several eggs in each tube, sealing them all individually. I think they resemble a rolled cigar inside. They will now stay there until next year when they will hatch out as more leaf cutter bees and fly away.