Japanese Beetle - The beetle species Popillia japonica is commonly known as the Japanese beetle. It is about 1.5 cm (0.6 inches) long and 1 cm (0.4 inches) wide, with iridescent copper-colored elytra and green thorax and head. It is not very destructive in Japan, where it is controlled by natural enemies, but in America it is a serious pest of about 200 species of plants, including rose bushes, grapes, [hops], canna, crape myrtles, and other plants.