Leafcutter Bee cocoons found in my bee boards

This is the first time I have found a different cocoon in my bee boards. Normally I have Mason Bees, and their use of mud is quite amazing. But I was completely blown away when I spotted a home for a new kind of bee. They are solitary as well, and quite similar to the Mason Bees. Both work by themselves and not in a colony, they collect pollen and store them away for their brood. And they are only active for a few months a year. They are known as Leafcutter Bees, as they cut small pieces of leaves off plants and use them to build a home for their offspring.

Above is an example of my Mason Bee homes, quite different looking with all the mud. Mason Bees collect mud and clay to build homes, while Leafcutter Bees use fragments of leaves and glue them together with their propolis.

I started opening my bee boards yesterday and right away I started finding leaves stashed away in the boards. Though nothing complete just yet. I am guessing the Leafcutter Bee got confused, brought them in the wrong hole and then just left them there. Or maybe predator ate them before they could finish.. Not really sure.

These are just little cuttings of leaves, I saw the bees carry them in. They seem to show up a little later than the Mason Bees. Its quite the sight to see a small little bee carrying a leaf at least its own size, flying in the air with it under its belly.

I am unsure of what plant they come from, though I did spot some leaves last year with the tell tale sign of these bees. The way they cut the leaves lets you know they were there.

A picture next to my hand, so you can see the scale of them.

Eventually I came across some intact and fully built cocoons. It was quite the feat of engineering these little solitary bees pulled off.

Another tray with just leaf fragments and then a complete home to the right. I found about five of these, not sure how many bees are in each of these leaf clusters. From what I have read online I should not open them or soak them in water. So we shall just see what emerges next year if I am lucky enough to be right by them as they do.

You can pick them up but you must take care to handle them very carefully. I cannot clean them as I do the Mason Bee cocoons as they are not water proof and it would kill the bee larva inside. Instead I removed them from the trays and placed them in mesh bags, I will put them out during the spring time and hopefully they will emerge. But I must say I was quite excited to find a new kind of bee in the homes. Now I have seen three kinds using my bee boards, seeing Mason Bees use them along with Leafcutter Bees and even Giant Resin Bees. I was only expecting one kind when I built these so its quite the treat.