In an anthill, some ants carry food and build, while others just eat and reproduce. This isn't just laziness: it's two distinct types of ants. Workers are smaller, while freeloaders are larger. If freeloaders become too numerous, the colony falls apart, like a communal kitchen where nobody washes the dishes.
Scientists built a mathematical model of how ants move from one nest to another. It turned out that hostility toward strangers is the key to survival. Ants greet intruders from neighboring nests more aggressively than those from distant ones. Thanks to this, freeloaders cannot take over new nests, and workers maintain their majority.
The model was tested on data from the ant Pristomyrmex punctatus — a species with no queen, where workers lay eggs themselves. Hostility toward neighbors turned out to be not random aggression but a beneficial survival strategy.
In the ant Pristomyrmex punctatus, there is no queen: worker individuals lay eggs themselves, but the colony also contains freeloader individuals that do not work and only reproduce.