Insects are the vital pollinators and recyclers of ecosystems and the base of food webs everywhere. In the United States, scientists recently found the population of monarch butterflies fell by 90 percent in the last 20 years, a loss of 900 million individuals; the rusty-patched bumblebee, which once lived in 28 states, dropped by 87 percent over the same period. With other, less-studied insect species, one butterfly researcher told me, all we can do is wave our arms and say, 'It's not here anymore!'" The most disquieting thing wasn't the disappearance of certain species of insects; it was the deeper worry ... that a whole insect world might be quietly going missing, a loss of abundance that could alter the planet in unknowable ways. "We notice the losses," says [entomologist] David Wagner. "It's the diminishment that we don't see." Because insects are legion, inconspicuous and hard to meaningfully track, the fear that there might be far fewer than before was more felt than documented. When entomologists began noticing and investigating insect declines, they lamented. Like other species, insects are responding to what Chris Thomas, an insect ecologist at the University of York, has called "the transformation of the world": not just a changing climate but also the widespread conversion, via urbanization, agricultural intensification and so on, of natural spaces into human ones, with fewer and fewer resources "left over" for nonhuman creatures to live on. What resources remain are often contaminated.