The white lines on this Columbine leaf were made by 2 tiny agromyzid fly larvae called "Leafminers." Leafminers live inside the leaf between the top and bottom layers (I tell my students that it would be like them being inside a giant peanut butter and jelly sandwich and eating the filling but not the bread!). In the area where the egg hatches and the larva is small, the lines are small. As the larva grows and eats, the lines get larger. The tiny black dots are called "frass," a.k.a caterpillar poop. On the back side of the leaf is an opening where the adult fly exited after pupating.