Which is the most abundant group of animals?

In terms of numbers of species, the answer is insects. Although no one is really sure just how abundant they are, for new species are discovered almost every year.

Estimates of the number of different species of insect range from well over a million to nearly three million. Whatever the true number, there are at least three times as many different kinds of insects in the world as there are every other species of animal put together.

If you could place every single insect in the world on one side of a huge pair of scales, and every single animal in the world on to the other side, the insects would weigh more.