Abstract
A new hypothesis explaining the adaptive significance of bright autumn leaf colors argues that these colors signal tree quality to myrmecophilous specialist aphids. In turn, the aphids attract aphid-tending ants during the following spring, which defend the trees from other aphids and herbivores. In this context, other types of plant coloration, such as the color change observed in young and old spring leaves, may function as a signal of plant quality for aphids and other myrmecophilous hemipterans. If these plant colors are costly for plants, then vividly colorful plants would be required to invest more in growth than in defense; as a result, colorful plants may be more palatable for honeydew-producing hemipterans, such as aphids, scale insects and treehoppers, although the relative importance of hemipterans other than aphids may be relatively low. These hemipterans may be attracted to colorful plants, after which their attendant ants would protect the plants from herbivory. However, it is necessary to examine color vision in hemipterans to support this hypothesis.