This video from the USA says about itself:
Acorn ant (Temnothorax longispinosus) larva close-up and a worker feeding a larva.
Courtesy of Johannes Gutenberg University Mainz in Germany and World Science staff:
Slave ant “rebellions” found to be common
Sept. 27, 2012
Ants held as slaves in nests of other ant species often damage their oppressors through acts of sabotage, according to new research.
Ant researcher Susanne Foitzik of Johannes Gutenberg University Mainz in Germany said she initially noted the “rebellion” behavior three years ago, in findings reported in the April 2009 issue of the journal Evolution. More recent research, she said, has revealed that the phenomenon—seen among ants that are enslaved in order to raise their masters’ offspring—is widespread.
In three ant populations in West Virginia, New York, and Ohio, Foitzik explained, enslaved workers of the ant species Temnothorax longispinosus have been observed neglecting and killing the offspring of their slavemakers rather than caring for them. As a result, only 45 percent of the slavemakers’ offspring survived on average—little over half the survival rate of the slave species’ brood in its own free-living nests.
The American slave-making ant Protomognathus americanus is a “social parasite” of an ancient lineage that depends entirely on other ant species, called the host species, to survive. Slave workers care for the brood in parasite nests, bring food to their masters and feed them, and even defend the nest.
The ants become slaves when workers from the slave-making ant colony attack the nests of the species T. longispinosus, kill the adults, and steal the brood. Back in the masters’ nest, which can be in hollow acorns, nutshells, or twigs, the slavemakers exploit the natural brood care behavior of the emerging slave workers. The slaves feed and clean the larvae, the maggot-like offspring of their masters.
“Probably at first the slaves cannot tell that the larvae belong to another species,” said Foitzik. As a result, 95 percent of the brood survives the larval stage. But the situation changes when the larvae become pupae, or undergo their metamorphosis into the adult stage. “The pupae, which already look like ants, bear chemical cues on their cuticles [shell-like skeletons] that can apparently be detected. We have been able to show that a high fraction of the slavemaker pupae are killed by slave workers.”
The pupae are either neglected or actively killed by being attacked and torn apart, the researchers found. Several slaves at once may assault a pupa, which cannot move or defend itself during the pupal stage and is also unprotected by a cocoon—P. americanus being one of a number of ant species which, for unclear reasons, don’t make cocoons.
In parasite nests in West Virginia, only 27 percent of the pupae survived, and in the New York colonies, only 49 percent, Foitzik said. In Ohio, the survival chances of the American slave-making ant was a bit higher at 58 percent—but this was still well below the survival rate of 85 percent for pupae of the “slave” species when in their own free-living nests.
A question is precisely what members of the “slave” or host species achieve by rebelling.
“The enslaved workers do not directly benefit from the killings because they do not reproduce,” said Foitzik. But their free relatives in the surrounding area—which might very well be their sisters—indirectly benefit, she noted, as slavemaker colonies weakened by rebellions are less capable of successfully launching new raids.
Interestingly, Foitzik added, geographic differences in the slave species’ responses fit predictions of evolutionary theory that populations will evolve different traits in response to different pressures from their local environment. An example: while host ants in New York are very aggressive and often successfully thwart slave raids, West Virginian hosts profit more from the slave rebellion because, as genetic analyses indicate, the neighboring colonies are more often close relatives to the “rebels.”