That is a grub, the larva of one of the Scarab Beetles. The larger ones become the June Beetles that congregate around lights in June and the smaller ones become the Japanese Beetles.

if you only found one.. throw it on the driveway to feed some bird ...

there is some magic number per square foot of soil ... when they become a problem ...

ken

There are a lot more possibilities than just June beetles or Japanese beetles! Lets remember that the original poster is from California where JBs don't live.

Most of the Scarab beetles begin their lives as grubs. The green fruit beetle grub is common to compost piles in California and it might be a very good possibility.

The OP is in San Francisco. Japanese beetles aren't any where in CA, at least, not yet.

Got the same thing down here in SoCal... tons of them in my compost.

So, the big ass teal beetles I see flying around in Summer AREN'T June bugs? But, more likely, green fruit beetles?

Suggestions for control? I did incorporate DE in the pile a few days ago to hopefully kill off SOME of them.

Kevin

Good information. Thanks everyone.