This is the well known Diabrotica undecimpunctata. I photographed it while it was munching on the flowers in my backyard. Its species name, undecimpunctata, meaning "11-spotted", refers to the 11 spots (or 12, depending on how you count the two adjacent uppermost spots) on its elytra (fore wings).
Beetles (Coleoptera) are the most speciose group of insects. In fact, almost 30% of all known animal species are beetles according to this web site. The oldest beetle fossils are about 265 million years old.
morphology and evolution of beetles
The fossil record of major insect groups