Ravenous little bastards. Japanese beetle, as others have noted.

Out on the western slope they got them under control by collective action. Takes a combination of nematodes and fungi for the larvae in the soil, and judicious use of traps to draw adults out of the desired area. There are plans to introduce one of its natural predators in order to control it.

Edit: CSU has a lot of helpful info here

2nd edit: A great Sun article on the topic here