By late October, Japanese Beetle adults in Indiana have died, but their larvae are still feeding under the soil. The C-shaped grubs have powerful mouthparts for chewing on the roots of grass. A grub often feeds in one spot until the roots in an area are all devoured. A grub will then dig with its mandibles and use its legs to push loose soil behind it. In this manner the grub can tunnel slowly through the soil. A Japanese beetle grub can tunnel over 6 meters in a month in search of food.
When the soil temperature drops, the grubs respond by tunneling vertically below the freeze line and spend the winter warm, deep under the soil. When soil temperatures rise, the grubs actively tunnel toward the surface to resume feeding.