I was walking in the woods when i saw the interesting patterns on the leaves of some elm trees and started photographing thrse abstract tunnels through the leaf. It took me several shots until i realized there were still a good dozen of larvae on each leaf, eating it up. These are sawfly larva (Aproceros leucopoda), specializing on elm leaves. The german common name of this invasive species translates to 'zig-zagleaf-wasp', and obviously gets that name from the distinct looking tunnels it creates, while feeding on the elm leaves.