Lizards and snakes inhabit a world so richly textured in chemical info
rmation that, as primates, we can only imagine it. Subtle nuances of c
hemical shading underlie nearly every fundamental activity of their li
ves, from finding food to finding mates. Recent work examines the natu
re of these chemical messages, mechanisms for their perception, the in
terplay of the chemical senses in the sociobiology of the group, and p
atterns of chemosensory evolution. Emerging is a new sense of lizard a
nd snake behavioral complexity that belies the common notion of these
animals as simple automata and points to a surprising capacity for pla
sticity and learning.