In The Descent of Man, Charles Darwin proposed that an ant's brain, no larger than a pin's head, must be sophisticated to accomplish all that it does. Yet today many people still find it surprising that insects and other arthropods show behaviors that are much more complex than innate reflexes. They are products of versatile brains which, in a sense, think.

Fascinating in their own right, arthropods provide fundamental insights into how brains process and organize sensory information to produce learning, strategizing, cooperation, and sociality. Nicholas Strausfeld elucidates...