system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If flies don't bite, why does it hurt when they land on you?
gpt
While some kinds of flies do bite, what you're likely feeling is the hairs on their feet that can be irritating especially to sensitive skin. Flies have adhesive pads on their feet called pulvilli that consist of tiny hairs that have spatula-like tips. These hairs produce a glue-like substance made of sugars and oils that help them stick and can irritate some people's skin.