The "KEY TO THE NEARCTIC SPECIES OF HOPLIA" - found via here (1) - lists four species of Hoplia beetles west of the Rocky Mountains.

The black color at first had me thinking possibly Hoplia hirta, pg. 5 of the key. But H. hirta has a bilobed clypeus, which does not seem to be apparent with this specimen. H. callipyge may also have a dark integument, but never a bilobed clypeus, pg's 16-17 (1). There are no confirmed images of H. hirta on the guide yet, and no black images of H. callipyge - for comparison.

These black hoplia June Beetles are sometimes fairly common around our "lawn" in April and May, where I suppose the larvae have been living and feeding on the lawn roots. Only H. callipyge is mentioned as a lawn feeder - pg. 15.

Also, these black Hoplia beetles always emerge earlier than the lighter colored Hoplia beetles that emerge in my yard later in the season (2) (3).

Any comments or help with possible species ID is always appreciated!