Answer:
Maintenance of homeostasis usually involves negative feedback loops. These loops act to oppose the stimulus, or cue, that triggers them.
Monarch caterpillars consume milkweed plants and Viceroy caterpillars eat willows. You can tell the difference between the two now by their flight patterns. I would say the answer to your question is that though they are similar, Viceroy were the “uglier” for the simple reason of survival. Predators would find their coloration as un-tasty.