The word "armadillo" is Spanish for little armored one. This midsize mammal that looks like a walking tank is a source of fascination for many people but a mystery to almost all. Dating back at least eleven million years, the nocturnal, burrowing insectivore was for centuries mistaken for a cross between a hedgehog and a turtle, but it actually belongs to the mammalian superorder Xenarthra that includes sloths and anteaters. Biologists W. J. Loughry and Colleen M. McDonough have studied the nine-banded armadillo ("Dasypus novemcinctus") for more than twenty years. Their richly illustrated...