While I was putting away my bee boards for the season, one of them came apart. I left it outside to observe how the larva goes through their transformation.
At this point they have eaten most of their pollen left behind by the adult female mason bees. Next is for them to start spinning a cocoon around them. Then they will lay and wait for the follow year and emerge a fully formed Mason bee.
In the animation above we can see the mason bee larva working silk to make a bean shaped cocoon that will allow it to pupate and form into a bee.
The boards they are living in are custom made in my garage using a wood router. I find this design to be the best way to manage solitary mason bees.
Normally these larva would be in complete darkness, closed up by the adult female mason bee that laid the larva. Every female in that species is a queen.
Some of the larva tumbled out of their cell and did not make it. This would not normally happen if I did not open the boards. But many stayed in their cells even with the roof removed.
At the front of the tray, some of the larva were still busy eating the pollen left behind. They will eat it to grow and then spin the cocoon once its all consumed or they have ate enough of it. They are yellow from rolling around in it and such.
The cells are made of mud, this is where the bee got its name "mason bee" as they work with mud to make homes.