Uncle John knows pretty much everything—and if he doesn’t, he heads his massive research library, or puts one of his many associates on the case. So go ahead: In the comments below, ask Uncle John anything. (And if we answer your question sometime, we’ll send you a free book!) This week’s question comes from reader Lisa P., who asks…

What is the purpose of a gnat?

Ah, summer. Barbecues! Trips to the beach! Tiny, annoying insects buzzing around your face and flying up your nose! Yes, the gnat is as indelible a part of summer as the Fourth of July and sunburns, but they really do serve a purpose in the intricate web of nature.

Similar to how sardine is an umbrella term for any number of small, can-worthy fish, no one single bug is a gnat. There are dozens of species in three different flying insect families, although the one you’re thinking of is the common gnat, or Culex pipiens, a relative of the more volatile but equally annoying mosquito.

Gnats travel in swarms (called ghosts) around stagnant water, forests, and your facial orifices. Not only that, but they’re especially fond of feasting on houseplants, from the leaves down to the roots, killing them slowly before you even know the damage has been done.

So just how does the gnat justify its existence? The purpose of a gnat is to get eaten by creatures higher up on the food chain that are a little less annoying to us humans: birds and bats, mostly, although some other insects eat gnats. They also pollinate flowers that grow in moist soil along waterways.

However, to the gnat’s credit, they don’t eat blood like their mosquito relatives. Some gnats live for just a few days and don’t even eat at all during their short lives. That’s because they feast in their larval state, on fungus and algae, which can be invasive.