Saturniid moths also have specific host plants. Although exceptions exist, several key characteristics or traits, typically used to separate and identify butterflies from moths, are illustrated in these drawings. Most butterfly species lay their eggs singly, one egg per leaf. Eggs hatch in a week or two. Newly hatched caterpillars are small and can grow for days unnoticed.
Most caterpillars are selective about what they eat.
They feed on only one or two host plant species. Throughout their development, almost all butterfly caterpillars remain on the plant where their eggs were laid, or move only short distances to feed on other suitable host plants. Larger, more visible caterpillars also may display characteristics designed to protect them from birds and other enemies. Monarch larvae feed heavily on milkweed and accumulate toxins called cardiac glycosides in their wings and bodies. The bright and distinctive markings of these colorful butterflies tell potential predators that their taste is bitter and the predator would be better off leaving them alone.