This leaf is almost eaten by the insects. They eat the leaf as following the frame clearly it should be a good reference how to eat it. You're able to identify the condition of the leaf with the trace of eating because the insects know what the nutritious leaf is. When you see each leaves on the tree (or the plants) , you can find out different conditions of the leaves. The leaf is convenience tool and food are able to use as hiding place, foundation of the eggs and materials of the nest etc.