Corn Flea Beetle
Corn flea beetles are small, shiny, jumping beetles that strip the upper surface from seedling corn leaves. Injury is most likely to occur on two- to four-leaf stage corn when cold temperatures slow growth.
Source of information
J.P. Michaud (http://entomology.k-state.edu/extension/insect-information/crop-pests/corn/fleabeetle.html)
Pest photo source