Ground Bees

There are several kinds of bees that dig and nest in the ground. Some like Cicada Killers dig out a single hole, leaving what looks to be a mound of dirt or sand, and kills a cicada and buries the cicada and the bees egg in the hole. Cicada killers are very large looking bees, but they generally won't bother humans unless provoked. Some ways to control them would be to keep your lawn thick and well maintained to prevent the Cicada killers from finding adequate areas to nest or in some cases a chemical treatment will be necessary. Professionals often times will dust the holes or do a power spray. This treatment will need to be followed up on the follow year.
Another ground bee is known as the digger wasp. These wasps can appear to be hovering over the lawn and can appear in great numbers at times. They are not an aggressive wasp generally and the control is similar to the cicada killer, and that is to dust the holes or apply a broad range pesticide.
The ground nesting bees to watch out for are bumble bees and yellow jackets that will nest in abandoned rodent borrows or other holes in the ground. These bees are very aggressive and will attack and cause harm. Before mowing your lawn be sure to survey the lawn to make sure there is no bee activity coming or going from the ground. This is often the way humans are attacked. The above picture shows what a yellow jacket nest under ground can look like. These nests should be handled by professionals. They will most times dust the entrance hole using a dust stick to keep a distance and treat the holes this way. Do not use gasoline to try to kill them yourself. This is dangerous and will contaminate the ground.