I found a vertical mud tube about the thickness of a pencil in my garden with a series of metallic green insects coming out of it. They came out when I pulled a weed but stopped when I stopped, as if the vibrations were scaring them out. I think they were bees, wasps, or flies. They were 1/2" long or a little longer and thin. Head, thorax, and abdomen were all shiny green, wings transparent. What are they?
I live near Philadelphia and it was in the upper 60s F today.