What are animals without backbones called?

Invertebrates, and it is the least useful category in biology - a group defined entirely by what it lacks. It covers about 95 per cent of known animal species, including insects, spiders, crustaceans, molluscs, worms and jellyfish, which are no more closely related to each other than any of them is to us.

Calling them invertebrates is like sorting the world into elephants and non-elephants. An octopus and a beetle are separated by more evolutionary distance than a beetle and a human, and lumping them together makes sense only from the specific and rather self-regarding perspective of an animal that happens to have a spine.

The numbers are the argument. Beetles alone account for around a quarter of all described animal species. Insects may outweigh all wild vertebrates combined, and nematode worms are estimated to be four out of every five individual animals alive. Ecosystems run on pollination, decomposition and soil turnover done almost entirely by animals in this category - and conservation funding follows charisma, so almost none of it goes to them.