Why are there so many different kinds, or species, of living things on earth, each uniquely fitted to its environment? For Charles Darwin, this question represented the "mystery of mysteries." Darwin first began to formulate an answer during a youthful voyage around the world on the H.M.S. Beagle from 1831 to 1835. Darwin's answer, known as the Theory of Natural Selection, changed the way we think about life on earth. In a clever twist, this beautifully illustrated and engaging account reveals that Darwin had help from an unlikely source: a beetle named Rosie, who possessed a very un-beetle-like urge to see the world. Rosie the Beetle accompanied Darwin on the now-famous voyage of the Beagle. Her lively, witty narrative describes how she took Darwin under her wing, providing clues and hints that guided his insights. The young reader is challenged to use the clues to solve the mystery before Darwin does.