Brad, There are over 20,000 species of bee in the US. Some live in the ground, some live in holes they bore into wood and others build homes above ground.

If they lived in the ground under the shed and you enclosed that space with your green house you probably trapped them. If you could leave the door or a vent open they will be able to get out and relocate.

Good Luck.

Well
i did some reading, and looking at the wood.
I found like 20+ holes about 1/2 inch wide.
lots of sawdust.
I remember seeing a huge amount of sawdust before in the old shed.
This structure is only a few months old, but there are a few of the larger crossbeams remaining that were from the old structure. But, even the new stuff has a bunch of holes in it.

They are mating too, i can see 2 of them together while flying

I need to figure some way of building, luring them into a trap.

i can open the door and let them out, but i think they are small enough to find a place to squeeze back into, its not perfectly sealed.
Normally, when i open the door, only 1 or 2 will fly out anyway. most stay in the greenhouse.

greenman62. It looks like those may be mason bees. I'm pretty sure that I had them in my garage also. Before I enclosed the open carport half of my garage I saw them. They were in the 2x6 joists on the roof. When I enclosed the area for my wood shop they were only able to live until the sealed brood hatched out. But if it is warm enough in your greenhouse to support them over the winter they could be an ongoing problem.

I never have tried to remove them from a structure. Like you said it would be difficult to trap or exclude them. They drill about 6" holes and lay a series of eggs to the end of their tube. You can kill them by running a 1/4" rod to the end of the tube. I would think you could trap them then releases them after they hatched by stapling a brown paper bag over each hole. Either way it will take a lot of time to get the situation under control.

Maybe someone else has dealt with this before and can tell you what they did.

Good Luck