tumbling flower beetle, (family Mordellidae), any of about 1,500 species of beetles (insect order Coleoptera) named for their jumping, turning, and tumbling motion when disturbed or caught. These black beetles are small, usually between 3 and 7 mm (0.1 to 0.3 inch) in length, and are most often seen on flowers. They are covered with fine hairs and are humpbacked and wedge-shaped, with a broad anterior end tapering to a pointed abdomen that extends beyond the forewings. The larvae live in and feed on rotten wood and plant stems.