system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What are those swarms of bugs actually doing when they seem to just be flying around in a small area?
gpt
Could be for various reasons, depends on the situation, species, etc.

Usually it's somewhere with a damp breeze (downwind of a river or pond), and food.  They see something you don't and are hanging around where the food is for them.

Another reason is a mating swarm.  At certain times of the year some bugs swarm up to make the task of finding mates a lot easier (basically like a big mixer).