Ok, I give -- where are all the bees?

I live in SW Ohio, Zone 6. EVERY year, without fail we have bees galore --
honey bees mostly, but a fair smattering of bumbles as well. This year, all
of my trees and plants bloomed beautifully. I let the grass and weeds grow
in -- they all bloomed (the wild violets nearly covered my front yard -- it
was amazing). The Crab Apple had a HUGE display. In any other spring
season, these trees and plants are just COVERED with bees -- when we walk
down the sidewalk to the cars, we have to dodge the bees they're so
plentiful.

This year, I have seen TWO bumble bees -- both of them inside my parents'
house. That's it -- I have seen a few wasps, a few hornet/yellow jacket
types, and that's it. I've seen no pollinators at all. The trees have lost
their blooms and are leafing out (if not already fully leafed out), the
weeds have lost their blooms, and the early blooming flowers are gone.

What one earth happened to the bees?

James