undesirable lover; bad boyfriend/girlfriend
Idiomatic expression for a romantic partner one's family or friends disapprove of; often used in the phrase 悪い虫がつく (to get involved with a bad lover).
I'm worried that my daughter might get involved with an undesirable lover.
Refers to a fit of anger or strong emotion; often used in the phrase 悪い虫が起こる (to get into a temper). Somewhat dated or literary.
He suddenly flew into a rage as if seized by a fit of temper.
Formed from 悪い and 虫, using 虫 in its traditional figurative sense of an inner impulse, passion, or troublesome influence.