The white grubs you find in your lawn this time of year are larvae of the native June bug or June beetle, or less likely but possibly, the European chafer or Japanese beetle. These grubs are particularly fond of the fibrous roots of lawn grass. You might not see the damage caused by these pests until later in the summer, so now is the time to take action before large brown patches of ruined lawn emerges.
If your lawn can roll up like a carpet (a decimated root system), there may be a grub infestation. It takes only 8 or 10 grubs to ruin a square foot of lawn. Your lawn may feel spongy to walk on or skunks and other small mammals are digging up your lawn at night. Typically these infestations don’t happen every year because it takes three years for the June bug to mature, so the damage happens cyclically.