Because the adults feed heavily on foliage of a wide range of ornamental plants, fruit trees, vegetable plants, and shade trees, they are very serious pests independent of the damage done to turf by the grubs. They are striking insects, colored a brilliant metallic green with coppery brown forewings that do not quite reach the tip of the abdomen. There is a row of five white spots along the side of the abdomen and a pair of white spots on the top of the last abdominal segment that distinguish this beetle from similar species such as the Green June Beetle. Biology Japanese beetles have a single generation each year. Adults appear in late May and may be active into July.
Adults live four to six weeks and females lay eggs during most of their lives.
Eggs hatch in about two weeks. Maturing in the fall, the grubs overwinter in the soil and resume feeding in the spring. After two to four weeks, the grubs mature and pupate in cells in the soil. Adults emerge three to four weeks later and remain in the cells for several days before digging to the surface. Adults are active during the day, returning to the turf in late afternoon.