what species of bee?

[afss]

A co worker has a lot of these on his lawn after he mowed and was wondering what they are. A bit smaller than a dime.

[Barry Digman]

It looks like a typical solitary bee that is ground nesting. Look up "solitary bees" and check the images to see if something pops up for your area.

[samak]

I wonder if they are some type of mining bee that makes nests in the soil?

[GaSteve]

I believe they are miner bees. The ones I see here make dozens of pencil size holes usually in sandy soil and are extremely docile.