Here are a couple of pictures from Larry Ginger of “American Lawn Care” in Des Moines. It is of grub damage in Urbandale, Ia from October 24, 2012. I believe that this is a Masked Chafer grub.
While grub damage is not unusual in Urbandale, the timing is somewhat unusual. I would expect to see first damage in August and I would expect the damage to be over by early October. At that time, the grubs generally burrow down about 6 inches in the soil to overwinter.
This is unusually late to see active grubs, but there have been a lot of unusual things this year. I have had a couple of other calls on late grub activity. If anyone else is seeing it even later, send me some pictures and some information on it siting so that we can keep a record of it on the blog for next year.