Commander's caterpillar

It eats both sides of the midrib of a young leaf leaving the latter projecting as a dry filament. It sits on the bare rib, indistinguishable from frass (powdery material phytophagous (plant-eating) insects pass as waste after digesting plant parts). It rests on the upper surface of the leaf when it’s matured with its body curled into a close C-form and the tail often strongly elevated. Its body coloration gives an appearance of lump of moss sticking to the leaf.