Knowing your nematodes

A few bad nematodes have maligned the whole class of creatures. While gardeners curse the nematodes that knot their carrots or riddle their tomatoes' roots with tumors, a much larger world of nematodes is at work defining our planet.

These largely microscopic roundworms are so ubiquitous and varied that nematologist Nathan Cobb described them as a means of mapping Earth: "In short, if all the matter in the universe except the nematodes were swept away, our world would still be dimly recognizable, and if, as disembodied spirits, we could then investigate it, we should find its mountains, hills,...