Idle Ants Have a Role

Using elementary distributed computing techniques we suggest an explanation for two unexplained phenomena in regards to ant colonies, (a) a substantial amount of ants in an ant colony are idle, and (b) the observed low survivability of new ant colonies in nature. Ant colonies employ task allocation, in which ants progress from one task to the other, to meet changing demands introduced by the environment. Extending the biological task allocation model given in [Pacala, Gordon and Godfray 1996] we present a distributed algorithm which mimics the mechanism ants use to solve task allocation efficiently in nature. Analyzing the time complexity of the algorithm reveals an exponential gap on the time it takes an ant colony to satisfy a certain work demand with and without idle ants. We provide an $O(\ln n)$ upper bound when a constant fraction of the colony are idle ants, and a contrasting lower bound of $\Omega(n)$ when there are no idle ants, where $n$ is the total number of ants in the colony.

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