potato beetle, name for two beetles of the leaf beetle family and for two of the blister beetle family, all destructive to the potato plant and its relatives. Most notorious is the Colorado potato beetle, or potato bug ( Leptinotarsa decemlineata ), a black-and-yellow striped member of the leaf beetle family. It was once confined to the Rocky Mts., where it lived on wild members of the nightshade, or potato, family. When settlers introduced the Irish, or white, potato (c.1855), the insect spread through most of the United States and then to Europe. Its orange-yellow eggs are laid in clusters on the undersides of the leaves, on which the reddish, black-spotted larvae feed. Pupation (see insect) takes place on the ground, and the adults emerge to feed on the potato plants; they hibernate underground during the winter. The destruction caused by the Colorado potato beetle has been one of the chief reasons for the development of insecticides; Paris green and other arsenic compounds have been used extensively. A member of the same family is the three-lined potato beetle ( Lema trilineata ) of the E United States, sometimes called old-fashioned potato beetle. The adults are yellow-orange with black stripes and lay their eggs scattered randomly over potato leaves. Two blister beetles of the genus Epicauta are also known as old-fashioned potato beetles. They are slender insects with complex life histories, passing through several larval stages before pupating. They feed on potatoes, tomatoes, and other members of the nightshade family. One ( Epicauta vittata ) has orange and black stripes and is also called striped potato beetle, or striped blister beetle; the other ( E. marginata ) is black with gray margins. The various potato beetles termed "old fashioned" were considered major pests before the spread of the more destructive Colorado potato beetle. Potato beetles are classified in the phylum Arthropoda, class Insecta, order Coleoptera. The Colorado potato beetle and the three-lined potato beetle are classified in the family Chrysomelidae and the old-fashioned potato beetles ( Epicauta ) in the family Meloidae.