Green Metallic bees
Discovered this patch of dirt in my yard with two holes in it. After observing for a minute an iridescent green bee flew down and went down the hole. So I grabbed the camera and staked out the entrance. They're very timid, they poke their heads out of the hole, and if they see you, they scoot back down. The fine folks over at the Insect Macro Photography group identified them as Green Metallic Bees (Agapostemon splendens).