Science: Selective Service Underground

How ant colonies draft their soldier armies and maintain balance in their incredible caste systems was cleared up last week by a Chicago zoologist. The secret: a "social hormone" exuded by some of the ants to inhibit the others.

Of all the social insects,* ants are the most highly developed. As many as eleven castes stratify some ant species: even the simplest colonies contain queens, drones, workers, soldiers. The drone caste contains all the colony's few males, whose sole function is sexual. So is the queen's. But the workers and soldiers are all sterile....

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