what is their purpose?

Why are gnats on this planet? What purpose do they serve, other than to annoy us? They appear as if from nowhere, as though they are created out of thin air. They are so tiny, yet are so distracting. I loathe them. Unless someone can prove to me that they do serve a significant purpose that no other insect can accomplish, then I will continue to despise & disrespect them. At least flies serve a purpose, as nasty & filthy as they are. If it weren't for flies, then this planet would smell ripe with death. Yuck!