worker bee
Refers to a female bee that does the work of the hive.
働き蜂は蜜を集めるために飛び回る。
Worker bees fly around to collect nectar.
hard worker; diligent person
Colloquial metaphor comparing a hardworking person to a worker bee.
彼は会社の働き蜂だ。
He is a hard worker at the company.