Late in summer, perfect little round holes with small mounds of spoil around them start appearing throughout the garden. These are the burrows of the digger wasps. The adult wasps work tirelessly to excavate tunnels and underground chambers. They dive into the hole head first and emerge a few minutes later with a little bundle of earth that they carefully move out of the way of the tunnel entrance.
The wasp grubs will over-winter deep down in the tunnels, feeding on a larder of food the adult wasps provide for them. Then late next summer, new wasps will emerge and the cycle starts all over again.
These solitary wasps are not aggressive and I’ve never known of one stinging a human. They do have a sting, but they only use it for paralysing their prey – mostly flies.
It’s a bit sad that when you look for information on the internet about garden insects many of the results will be about “control” methods: and that’s the case with digger wasps too. Yes, they do make holes and little mounds of earth, but they do no damage to your grass or plants. There is certainly no need to “control” them: you might even be grateful to them for eating up some of your houseflies:)