From G.B. “I was splitting wood and discovered leaf like cocoons. They are about 1 inch long. Not quite the same size as the purchased leaf cutter bee cocoons. Would you please let me know what these are? Photos attached…. ” These are leafcutter bees. The native leafcutter bees are often a bit larger than the commercial species. The picture of the wooden cavity is an awesome picture. I wonder what insect burrowed into the wood originally? Likely a beetle species.