To me it looks like a Japanese beetle larva (I'm not an expert).
A bacteria called Milky Spore will kill the grubs. The grubs will eat numerous varieties of plant roots and stunt their growth or even kill them outright, probably not what you want in your lawn and flower gardens. Sissy is right, moles eat them and if there is mole food, the moles will come, sometimes right through you pond liner!
If memory serves me correctly you apply Milky Spore a couple times the first year, then your protected for a long time. Milky Spore only effects grubs so it's very safe.