I have recently submitted a caterpillar that appears to be identical to this but in a green colouration. I’m assuming it is the same species, but curious about the colour, is it possibly due to the plant it is feeding on?
C. senilis larvae appear to have the dark dorsal line extending along the full length of the caterpillar. In later instars of C. cuculloides, the dorsal line shrinks to be just over the thorax and first abdominal segments. The colour varies from green through yellow to orange and red. It is unclear why.