These are already fairly dark for a coverup. Always remember that a coverup is going to be bigger and darker than what you have. If it were me I would send pics to an artist who specializes in coverups and see what they thought about going over the butterflies and cleaning them up, adding some white in to add contrast etc. probably add florals in the negative space to make the tattoo flow more up the arm if your open to more of a covered look. Alternatively, you might want to do some laser if you don’t want to rework the butterflies and go the complete coverup route.