wouldn’t hurt a flea – wouldn’t hurt anyone

have a bee in one’s bonnet – be maniac about sg.

as busy as a bee – very busy doing sg.

ants in your pants – agitated, restless due to excitement

drop like flies – die or collapse in big numbers

as snug as a bug in a rug – feel very comfortable, cosy

make a beeline for sg. – go directly towards sg.

put a bug in someone’s ear about sg. – give sb. a hint about sg.

fly in the ointment – snag, a small but important problem

have butterflies in one’s stomach – feel nervous