to mimic "client fleeing" in natural settings. In other trials, the plate of their preferential food source chased the cleaner fish when they eat it, mimicking "client chasing" in natural setting. After only six learning trials, the cleaners learned to choose against their preference, indicating that punishment is potentially a very effective countermeasure against cheating in mutualistic relationships. Finally the countermeasures are not limited to organismal relationships. West et al. found a similar countermeasure against cheating in legume-rhizobium mutualism. In this relationship, nitrogen fixing bacteria rhizobium fixes atmospheric N2 from inside the roots of leguminous plants, providing this essential source of nitrogen to these plants while also receiving organic acids for themselves. However, some bacteria are more mutualistic, while others are more parasitic because they consume the plant's resources but fixes little to no N2. Moreover, these plants cannot tell whether the bacteria are more or less parasitic until they are settled in the plant nodules. To prevent cheating, these plants seem to be able to punish the rhizobium bacteria. In a series of experiments, researchers forced non-cooperation between the bacteria and the plants by placing various nodules in nitrogen-free atmosphere. They saw a decrease in the rhizobium reproductive success by 50%. West et al. created a model for legume sanctioning the bacteria and hypothesizes that these behaviors exist to stabilize mutualistic interactions. Another well-known example of plant-organism interaction occurs between yuccas and yucca moths. The female yucca moths deposit their eggs one at a time to the yucca flower. At the same time, she also deposits a small amount of pollen from yucca flowers as nutrition for the yucca moths. Because most of the pollen is not consumed by the larva, yucca moths are therefore also the active pollinators for the yucca plant. Moreover, sometimes the female moths do not successfully deposit their eggs the first time, and may try again and again. The yucca plant receives scars from the multiple attempts, but they also receive more pollen, since the moths are depositing pollen with every try. "Cheating" sometimes happens when the yucca moth deposits too many eggs in one plant. In this case, the yucca plant has little to no benefits from this interaction. However, the plant has a unique way of constraining this behavior. While the constraint against cheating often occurs directly to the individual, in this case, the constraint occurs to the individual's offspring. The yucca