"This engaging STEM offering has applications that cross curricular areas, provides accessible models of how scientific inquiry works, and introduces a couple of pretty cool scientists as well as a plethora of caterpillars." -- Booklist (starred review) This is a story about remarkable creatures, inquisitive people, and fascinating conversations. The creatures? Pine processionary caterpillars with mysterious group habits. The people? Jean Henri Fabre and, many years later, Terrence Fitzgerald--scientists with big questions about the behavior of these caterpillars. And the conversations? The conversations span lifetimes, as one researcher continues a dialogue started by the other. In this playful, candid, and accessible book for young readers, biologist Loree Griffin Burns captures the unique leader-follower behavior of pine processionary caterpillars through a glimpse into the "ask, test, repeat" nature of the scientific process--and shows how that process creates one long line of questioning and learning. Back matter includes more details about the two scientists as well as a glossary, bibliography, source notes, and suggestions for further reading.