Perhaps the most hyper-diverse group of animals in the world are the chalcid or jewel wasps. They don't sting, they lay their eggs in others, including others eggs (some eggs of things so small they were only recently proven to be the hosts), as parasitoids (things that kill their hosts). They are everywhere, it's trivial to catch them on any front lawn with the right techniques, yet the vast majority of people would never know they are there. The broader lineage include some species smaller than the largest amoebas.
If you want to see ecology in a nutshell look at fig wasps, absolutely insane, soldier-like males, blind, wingless, ant-like males of other species, variable length ovipositors that let them exploit all different micro-micro areas of a fig. Multiple inter-dependent species on one species of Fig? Sure, why not. It goes on ad-nauseam.
https://chalcid.org/ for a classic picture in our field.