MILEY CYRUS pulled her usual shtick at the iHeart Radio Music Festival in Las Vegas Saturday.  She wore two different outfits . . . and both were pretty well, adult.

One was a see-through mesh mini-dress . . . under which she wore nothing but bikini bottoms and PASTIES.  

She also brought some LITTLE PEOPLE onstage with her . . . including that blonde girl who TWERKS.  Miley slapped her ass, of course.