Only ding bats drop the mail scales, the mouse bats do not. At least, I havent seen them do it. They drop them fairly often, which is annoying if youve done the quest and dont need them anymore...
don't even bother to post anything like that again. plus, a stack of 12 bat wings can get you 1200 gil and fame in san D'oria, so don't sell em, save em.