What is the best exercise for the arm bat wings?

I have a question for those who can help. I am trying to figure out what is the best exercise for arms. I am building muscle with my biceps, triceps, and shoulders with the strength training classes I am taking plus Zumba and Ripped for cardio. I increased my weights now but what is the best exercise for the bat wings? My mother is skinny and she has them and so did my grandmother. Can it also be genetic? I know I need to loose quite a few pounds so just continue and eventually they will get smaller?