Northern Masked Chafer - Cyclocephala borealis
This is the bum of a northern masked chafer larva (grub). To identify them to species, you have to examine the pattern of hairs and the shape of their anus. Not kidding. I had a summer job in grad school where I spent most of each day identifying beetle grubs, which involved staring at their butts and getting pooped on. The raster pattern (hairs) indicate that it is Cyclocephala borealis.
Habitat: In soil, under rotting wood
''Cyclocephala borealis'', the northern masked chafer, is a beetle in the family Scarabaeidae. It is native to North America, where it is considered a crop pest.