The concept of aposematism, especially in regard to butterflies, is discussed in terms of the close interrelationship between butterflies, as prey, and birds, as their predators, in their common environment. Vision, in a broad sense, and especially in terms of the visual capabilities of the avian eye, is discussed as a basis for understanding the difference between the aerial hawker insectivorous bird predators of butterflies, and all other birds, regardless of whether considered primarily insectivorous or not. The marked differences in foraging behavior determine how a bird perceives the bright color patterns of butterflies. For aposematic color patterns to be effective, they have to be seen by the bird as an optical device advertising distasteful or toxic qualities of the potential prey so that the predator avoids them by sight. It is argued here that birds that prey on butterflies do not perceive them as an aposematic insect, as postulated by the concept of aposematism. The bird does not reject a butterfly on the basis of color pattern, but on the basis of characteristic morphological and behavioral patterns which provide the bird with a signal as to whether the butterfly is energetically profitable or unprofitable for the bird as a food source.
