Slave-Making Ants

The other day I learned about an interesting new species of ant, the Formica sanguinea. This ant has the unique ability to secrete formic acid which is an adaptation that allows them to behave rather uniquely as a species. This ant is most interesting because it is a slave-maker ant, meaning it is an ant that makes other species of ants its slaves. Colonies of this ant can either live on their own or be parasitic.

To start an enslaved colony, a fertilized F. sanguinea queen enters the nest of the host ant species and kills their queen. She then will make all of the workers of the host colony tend to her brood, essentially enslaving them. Then, the F. sanguinea workers will be free to raid nearby nests. This raid entails of stealing the other colonies’ larvae and pupae which are taken back to the nest and forced to become future workers for the F. sanguinea. Not only to these raids provide workers, but they also provide food! If a member is killed during the raid, individual ants will carry that carcass back to the nest to be eaten later.

During a raid ants will dig and fight at the target nest. Then both slaves and slave-makers will carry brood back to the slave-maker nest. Interesting fact, raids never take place on rainy or overcast days because the weather conditions decrease the effectiveness of alarm pheromones.

Chemical effectiveness is important because F. snaguinea use formic acid and substances from the Dufour’s gland as a chemical defense. The substances in the Durfour’s gland contain hydrocarbons that serve as wetting agents before the formic acid is released. These substances in conjunction with one another dissolve the fat compounds of the epicuticle and they enter the tracheal system to kill opposing ant.

F. anguinea can tell if an ant is opposing or on the same team by analyzing the hydrocarbons on the cuticle of another ant. Surprisingly, even though the ants can tell their own colony apart from others, they cannot tall when an opposing colony is pure F. ganguinea. This means when a mixed F. sanguinea ant colony and a pure F. sanguinea colony meet, there will be aggression and fighting. This is most likely because the identifying hydrocarbons change when individuals are in a mixed colonies.

Another interesting thing about this ant is that they are one of the few species of ants that are not eusocial. If you remember from my first post, eusocial groups have to have a caste system by which their social structure functions. They are not eusocial because scientists have never observed any occasions in which certain individuals raid and others forage. However, some individuals do have more Dufour’s gland compounds than others.

These ants can be found in Central and Northern Europe through Russia to Japan, China, the Korean Peninsula and also the United States. This ant is red and black with workers up to 7mm long, and this is what they look like:

Formica_sanguinea_-_lindsey