Superorganisms = organism

People like to talk about ants as ‘superorganisms’. Of course, we’re all kind of superorganisms, built out of a structure of captured cells and using home-grown bacteria to function. But when we talk about ants, wasps, and termites, we mean something else. Each insect on its own seems to be an independent organism – though they can’t all survive away from the colony – but in reality, the colony is the organism.

In PNAS, Hou et al. apply the metabolic scaling law to eusocial insect colonies. Individual organisms have a metabolic rate that scales as the 3/4 power of body mass. Along with this are laws scaling reproductive organ mass, total biomass, and organism (colony) growth with metabolism. Individual ants do not follow this law: worker ants have almost no reproductive organs while the queen has tons of ’em.

The figure above shows the body mass vs. metabolic rate for some (non-ant/wasp/termite) insects and for various colonies as a whole. And the curves are the same! If you look at the other predictions, they all turn up exactly on the curve, too. So it is only when you consider the colony as a whole that eusocial insect act as a proper organism. Iain Couzin once mentioned to me that ants in a colony act analogously to neurons in a brain, though I can’t for the life of me remember how that was. But see, the individual ant is just like a lonely neuron: meaningless.