A housefly is a common flying insect with a gray body, red eyes, and transparent wings. You've probably seen dozens of them: they're the ones that buzz around kitchens, land on food, and seem impossible to swat because they dart away so quickly.

Houseflies can't bite or sting, but they're still considered pests because of where they land. Before visiting your sandwich, a housefly might have been crawling on garbage or animal waste. Their feet pick up bacteria and other microorganisms from these disgusting places, then transfer them to whatever they touch next.

A housefly's life moves incredibly fast. They hatch from eggs, transform from tiny maggots into adult flies, and can start reproducing in just a few weeks. A single female can lay hundreds of eggs, which explains why flies seem to appear out of nowhere when food is left out.

Houseflies have remarkable eyesight. Their large compound eyes contain thousands of tiny lenses that let them see in almost every direction at once. This is why it's so hard to sneak up on them. They also taste with their feet, which is how they decide whether something is worth eating before they even take a bite.