Figure 1

<div><p>Autumn Tree Colors as Warning Signals to Aphids?</p> <p>Two papers at the beginning at this decade challenged our view that the beauty of autumn leaves is only a by-product of physiological processes inside the doomed leaves [<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0050187#pbio-0050187-b013" target="_blank">13</a>,<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0050187#pbio-0050187-b014" target="_blank">14</a>]. According to the new hypothesis, trees with particularly strong coloration send an honest signal to aphids, informing them of the strength of anti-herbivore defenses of these trees. But to appropriately predict the responses of aphids to colors requires us not only to examine the physiology of their eyes (inset lower right: scanning electron micrograph of the eye of the black bean aphid Aphis fabae, courtesy of J. Hardie) but also their behavioral responses to colors under controlled laboratory conditions (inset, upper left: the foxglove aphid Aulacorthum solani probing a yellow artificial target; photo by S. Kirchner).</p>