。
Getting stung by a bee really hurts.
Literal
Bee [by-に] get-stung-[when-と] very hurts
Bee-sting passive: 蜂に刺される, with に marking the agent (the bee). The adversative/affective passive is common in Japanese for unwanted events — 'have the experience of being stung by a bee'. ~と here again sets up a generic 'whenever' condition.