Ants are well known for their hive nature, for their ability to perform complex behavior
s even though each individual ant has essentially no intelligence
. The features that allow for this complexity
-- chemical communication and innate support of fellow ant
s -- also make an ant colony the perfect environment for parasitic influence. Parasitic ants have evolved to take over the workers, habitat, and even queen of other ant colonies, subverting the victim colony
for the purpose of their own survival. These species of ants have generally specialized so much towards their parasitic purpose that they no longer have the ability to start or maintain a viable colony
, as opposed to one taken over from another species.
A good example is the Protomagnathus americanus ant of North America. Its victims are of the genus Leptothorax, as they all share the same chemical communication mechanisms that the Protomagnathus has learned to mimic. At any rate, a Protomagnathus queen that is mature and has mated (and thus is ready to have her own colony) eventually happens upon a Leptothorax nest. She enters the nest and starts attacking the workers within, by grabbing their antennae and dragging them out of the nest. This causes a danger signal to be sent down into the nest, which brings defense ants rushing out. The Protomagnathus queen is fast and strong, though, and expels the defense workers in the same way. All of this fighting leads to an overload of danger signal pheremone in the whole nest, which sends all of the Leptothorax ants into sort of a panic attack. They flee en masse, leaving their larvae, pupae, and food supplies entirely behind.
The larvae and pupae survive and mature on the food that is left behind, and the Protomagnathus queen bears her own brood. Since they share the same chemical signals, they get along well. The Leptothorax workers, which weren't mature for the nest takeover, serve the new queen as if she was their own as sterile slaves. Eventually the imposter queen bears a brood of new queens, which leave the colony to find a group of Leptothorax to take over for themselves.
Another interesting parasitic ant is the Teleutomyrmex schneideri. These ants have lost the ability to produce any kind of worker ant -- their broods are made up of only males and queens. They can survive only by parasitizing Tetramorium caespitum and Tetramorium impurum queens. The Teleutomyrmex queen can mimic the signals of Tetramorium queen well enough to enter the colony and find her way to the queen's chamber. She is also specially shaped to be able to attach to the queens back, and has glands that become sticky and take hold there. She does so, and spends the rest of her life there, feeding when the Tetramorium queen feeds, and breeding by the male offspring she was carrying when she attached. The worker ants from the colony mistake the Teleutomyrmex larvae for their own (since they came from the queen's chamber) and feed and raise them to maturity, when the females leave to find their own Tetramorium nest.
One final approach to enslaving other ants is that taken by the Amazon ant, Polyergus rufescens. They attack colonies in large numbers, and each secrete a danger signal pheremone that the colonies are sensitive to. Just as during a Protomagnathus attack, the danger chemicals push the victim colony into deep panic mode, and they flee the nest. Instead of moving in, the Polyergus raid the nest and take larvae back to their own colony, killing any workers who stayed behind to guard the larvae. The Amazon ants are unable to eat or build by themselves, and rely on the harvested slave larvae to do this for them. Their only chance of surviving as a colony is thus continued parasitism.