But you'd be forgiven for thinking it is. The swallowtail caterpillar in its early life stages hides from predators by disguising itself in the unappetizing black and white of bird droppings (as in two of the three larval stages shown here). It then makes a brief appearance in leafy green duds (the third larva) before transforming into a butterfly. Japanese researchers have found that the midlife color change occurs thanks to a drop in the level of so-called juvenile hormone. They could block the change to green by treating caterpillars with a similar compound, they report this week in Science.