Why do stink bugs smell so bad?

Answer: Chemical defense against threats

Poor hygiene from living dirty — Wrong. Stink bugs are actually quite clean. The terrible smell is a deliberately produced chemical weapon, not from being dirty.

Smell attracts their mates — Wrong. The smell repels, not attracts! It's purely defensive. Stink bugs do use pheromones to attract mates, but those are different chemicals and don't smell bad to them.

Chemical defense against threats ✓ — Correct! When threatened, stink bugs release aldehydes and other chemicals from thorax glands—smells like cilantro gone rancid! This odor warns predators 'I taste terrible!' The chemical also irritates eyes and noses. It's so effective that birds and lizards learn to avoid stink bugs!