Both of these beetles are well adapted to the climate of the northeastern states. The grub overwinters as a third-instar larva in the soil below the frost line. In spring it moves up in the soil to feed on roots for a short time. It then pupates for one to three weeks within the cast skin of the grub. This covering splits as the insect matures, and the adult beetle is ready to emerge.
Pupae are very resistant to pesticides.
Japanese beetle adults crawl out of the ground in late June and early July. They can fly as much as a half mile per day. The adults will feed on the foliage of 300 species of plants, but they usually exhibit preferences for a few in particular, such as grape, raspberry, or roses. The beetles mate, and females are ready to lay eggs about one week after emergence. Within two weeks the eggs hatch into first-instar larvae that feed on roots for three to four weeks.