Brighter-colored paper wasps (Polistes dominula) have larger poison glands

We collected wasps from 30 different nests and photographed them to measure the brightness of warning coloration in the abdomen. We also measured the volume of the poison gland, as well as the length, and the width of the abdomen. The results show a positive relationship between brightness and poison-gland size, which remained positive even after controlling for the body size and abdomen width.The results suggest that the coloration pattern of these wasps is a true sign of toxicity level: wasps with brighter colors are more poisonous (they have larger poison glands).Aposematic coloration is a defense system against predators widely used in the animal kingdom, by which potential prey use their striking coloration to warn a possible predator that they are toxic [1,2]. Aposematism has learning components, because predators learn to associate aposematic coloration with toxicity after testing the prey [3]. Thus, predators learn to avoid distasteful prey more quickly when the prey is more visible, as opposed to cryptic prey [4], which, in turn, impels a selective pressure for toxic prey to be as striking as possible, leading to a coevolution between predator and prey [5].Becoming and remaining toxic is likely to be costly for individuals, due to costs associated with the production or storage of the toxin [6]. In this case, once predators have learned to avoid aposematic prey coloration, an individual would benefit from having aposematic coloration and decrease the demands of toxicity [7]. This would cause the evolution of warning coloration to be evolutionarily unstable. In this situation, individuals within a population will honestly warn of their toxicity using warning coloration only if the signal is difficult to produce, so that a cheater would not be able to cope with such demands [8]. For example, since the warning coloration is striking, it would attract inexperienced predators, so that an individual with non-toxic aposematic coloration would be attacked with grea