The insects are a very important element in the chain of life. We have to remember that the smaller in size life is, the greater in numbers it is too. If you multiply size with quantity for every species you get the general idea that all creatures are of moreless of equal importance for ecosystems. Of course there are key organisms like the pollinating bees but who knows really what the hidden key role of a caterpillar is? Or of a certain becteria or fungi. The fact that it exists if you ask me, means that it has a key role, weather human sciance has figured it out so far or not.