The Viceroy is similar looking to the Monarch, but does not have the milkweed poison in its body. Birds that have had the bad experience of eating a Monarch will usually not eat a Viceroy. It is an example of Batesian mimicry. Or so it was thought; but recent work has challenged this. The difficulty in doing this kind of research is that a butterfly may be toxic in one part of its range, and good to eat in another part. A lot depends on the plants on which the eggs are laid.