One all-or-nothing approach to survival is to become essential to something else, to bind your fates so tightly that you live or die as one. In nature, such mutualism can entail risks, but it can also pay dividends by securing food and shelter for insects and their offspring. Mutualism takes many forms, the most extreme of which, coevolution, involves species influencing each other's evolution.
Insects and plants do not have a monopoly on coevolution or mutualism, but genetic research suggests that they have evolved in tandem virtually from the beginning [source: Misof et al.]. This long history has led to numerous hand-in-glove relationships between the two. Acacia ants live in the thorns of acacias and protect them from herbivores, while the trees' leaf tips provide food for the ants. Yucca flowers, for example, have shapes that only allow the yucca moth to pollenate them. After pollenating, females lay egg in the yucca. When they hatch, her caterpillars will eat some of the seeds but leave enough for rodents to disperse [source: Carter].