Solitary Bee Nesting blocks

So I made a few nesting blocks for bees.  I took a pine post and drilled 3/8" holes about an inch apart from each other.  There are already 10 complete shafts filled and counting.  This particular one is facing north, which is usually discouraged because of the cold temperature.  However, it is important to consider access, this hive looks directly over my garden, so it is no wonder why many have taken up residence there.  I have lilac bushes on the other side of the garden, which they are suppose to like.  I have also noticed notches taken out of the buckwheat I seed all over the yard, and the rocky mountain columbines I grew this winter indoors and transplanted.

So far I have identified a few megachilids and their leaf lined nests. The last picture appears to be a parasitoid wasp lingering around, but that's just a guess.