Here's why:
* Vast Diversity: Insects are incredibly diverse, with over a million described species and millions more yet to be discovered.
* Abundance: They are found in almost every habitat on Earth, from the deepest oceans to the highest mountains.
* Adaptability: Insects have adapted to a wide range of environments and food sources, contributing to their incredible success.
While other groups like fish and nematodes are also incredibly numerous, the sheer diversity and abundance of insects make them the undisputed champions in terms of number of species and individuals.