What is a night crawler? This is the basic question we are concerned with, and the answer is straightforward: a night crawler (also written as “nightcrawler”) is simply an earthworm, an extremely common worm we have written about dozens of times. After a brief refresher on exactly what earthworms are, we’ll explain why they are called “night crawlers” (or, again, “nightcrawlers”), and also list some of the other names that earthworms go by. Thus, our treatment of night crawlers and earthworms will be more linguistic than biological.