Not quite the guillotine, but ... Worker ants take turns biting the legs of a rebellious female ant to hold her down for days at a time.

No Sex for Rebellious Ants

In drama straight out of Hollywood, sex and power rule the world of the dinosaur ant. Ambitious female ants who dare try to usurp the ruling female are immobilized for several days by her minions, a new study finds. Once publicly chastised, the revolutionary loses all hope of ever reproducing.

Most ant societies are ruled by a single queen who is larger than the rest of her colony and designed specifically for high-production baby making. But among dinosaur ants (nicknamed for their prodigious size of up to 3 centimeters), all females are capable of reproducing. This is no free-love utopia, however. Only one female at a time is reproductively active and she rules the colony while breeding new generations. She defends her position with the aid of high-ranking enforcers. Her gang consists of the three to five females most likely to want her job, and she rewards their good behavior by exempting them from colony work. If anything happens to the ruling female, one of the gang will take her place. The problem is, the lure of power and sex can be enough to encourage an ambitious high-ranker to hasten along that succession.

Curious as to how the ruling female defends her position, entomologist Thibaud Monnin from the University of Sheffield, U.K., and chemical ecologist Francis Ratnieks of the University of Keele in Staffordshire, U.K., observed 18 colonies of dinosaur ants collected from Brazil. They found that when challenged for supremacy, the ruling female repeatedly rubs her stinger over the offending ant, smearing it with fluid from a gland in her backside. Loyal worker ants then swarm the traitor and hold her immobilized for up to 4 days. Once disciplined, the former insider has no hope of ruling the colony and meekly joins the working class.

The team sampled the oily fluid from different members of the power structure. Both the working-class and high-ranking ants can sometimes trigger the immobilization punishment, but the ruling female's fluid is far stronger. The pheromone fluid is composed mostly of chemicals called hydrocarbons, the team reports in the 5 September Nature, and the ruling female produces the highest percentage of hydrocarbons.

The dinosaur ant succession is reminiscent of the human power plays and conflicts familiar to watchers of daytime TV, says behavioral ecologist Kern Reeve of Cornell University in Ithaca, New York. "As we learn more about social insects," he says, "they seem less and less like robots programmed for cooperation and more like humans."

Related sites
Monnin's site
Reeve's site