【英语时差8,16】毛毛虫与植物（下）（在线收听）

 Scientists have known for some time that many plants protect themselves from insect attacks by producing toxins that either ward off or kill insects when they attempt to have the plant for lunch. What scientists have only recently discovered, however, is that the common caterpillar is not without its own arsenal of chemical agents. According to recent studies, a caterpillar can sense when a plant is about to unleash its chemical weapons and counter act by producing anti-toxins to neutralize the plant’s attack. So far, caterpillars seem to have the upper hand. Although different plants produce a wide variety of toxins, many ultimately rely on two main chemicals. Since caterpillars have evolved to neutralize these chemicals, they are able to infest over one-hundred toxin-producing plant species across the United States.