I’ve been delighting in the sheer breadth of information provided by Richard Dawkins’ The Ancestor’s Tale. It’s unfortunate that my biochemistry degree hasn’t required me to take a zoology course, but even if I had had a thorough zoological training, I think there would still be a number of species presented in The Ancestor’s Tale that would surprise me. Here’s a neat example: the leaf cutter ant.
Just as humanity did at the time of our Agricultural Revolution, ants independently invented the town. A single nest of leaf cutter ants, Atta, can exceed the population of Greater London. It is a complicated underground chamber, up to 6 meters deep and 20 meters in circumference, surmounted by a somewhat smaller dome above ground. This huge ant city, divided into hundreds or even thousands of separate chambers connected by networks of tunnels, is sustained ultimately by leaves cut into manageable pieces and carried home by workers in broad, rustling rivers of green. But the leaves are not eaten directly, either by the ants themselves (though they do suck some of the sap) or by the larvae. Instead they are painstakingly mulched as compost for underground fungus gardens. It is the small round knobs or “gongylidia’ of the fungi that the ants eat and, more particular, that they feed to the larvae…When a young queen ant flies off to found a new colony, she takes a precious cargo with her: a small culture of the fungus with which to sow the first crop in her new nest.
So, there’s complex, city-sustaining agriculture for you. Now how about keeping cows:
Several groups of ants have independently evolved the habit of keeping domestic ‘dairy’ animals in the form of aphids. Unlike other symbiotic insects that live inside ants’ nests and don’t benefit the ants, the aphids are pastured out in the open, sucking sap from plants as they normally do. As with mammalian cattle, aphids have a high throughput of food, taking only a small amount of nutriment from each morsel. The residue that emerges from the rear end of aphid is sugar-water–‘honeydew’–only slightly less nutritious than the plant sap that goes in at the front. Any honeydew not eaten by ants rains down from trees infested with aphids, and is plausibly thought to be the origin of ‘manna’ in the Book of Exodus. It should not be surprising that ants gather it up, for the same reason as the followers of Moses did. Btu some ants have gone further and corralled aphids, giving them protection in exchange for being allowed to ‘milk’ the aphids, tickling their rear ends to make them secrete honeydew which the ant eats directly from aphid’s anus.
I bet you never thought you could read a book on biology and get a lesson on ants that involve sBiblical history and graphic sex. Cheers!