And... they're back!
At first I thought this was a digger bee, but the antennae are so long.
I didn't dare to hope, but sure enough, this is indeed a male Summer Long-horned Bee Melissodes robustior.
See the yellow marking on the lower part of his face.
And such long antennae.
Their preferred flowers for pollen are sunflowers, cosmos, and tickseed such as this Coreopsis Big Bang Cosmic Evolution.