Why are there green stripes on the otherwise yellow and brown quaking aspen leaves?
If you look closely at the base of the green splotch, there is a brown pocket of leaf tissue and the upper petiole (leaf stem) is swollen. Who is inside?
A tiny and very hungry caterpillar! This 2mm long caterpillar secretes a chemical that prevents the natural deterioration of a section of the leaf. With chlorophyll retained and photosynthesis continuing, the larva keeps its food source alive. The caterpillar will exit the leaf to spend the winter as a pupa and emerge next spring as a tiny moth.