http://blogs.discovermagazine.com/discoblog/2008/08/18/enslaved-ants-revolt-slaughter-their-captors-children/
Many ants are known to be slave masters—their raiding parties steal the young from colonies of rival ants and raise the foreigners as workers in their own nest. However, Susanne Foitzik of Ludwig-Maximilians University in Munich may be the first researcher to study an ant slave rebellion.
The rebels are Temnothorax, tiny ants only about the size of the comma in this sentence. Their captors are called Protomognathus americanus, and despite being only a little larger, these bullies enslave the smaller insects. Inside the larger ants’ nest, which is built inside an acorn, the smaller ants are put to work caring for their masters’ young. But sometimes, Temnothorax slaves revolt against their servile existence and slaughter the Protomognathus larvae they’re supposed to be babysitting, as well as some of the enemy workers.