If competition between individuals was, scandalously, Nature’s way, she had forgotten to whisper the news to some of her smaller creatures. Many an ant species, Darwin knew, was divided into fixed, unbreachable castes. The honeypot ant of the American deserts has workers whose sole job is to hang upside down, motionless, like great big pots of sugared water, so that they may be tapped when the queen and her brood are thirsty.
