As fishtales points out, all flies are to some extent 'lures' as theyre not natural and aim to entice a fish to take. For the purposes of this thread though, and IMO i think a 'lure' is a fly that's not tied to deliberately replicate something natural. A blob for example is a 'lure' despite people saying they may look like a cloud of caenis.. A cat's whisker or Minkie is also a 'lure' as are the long tailed dog nobblers and indeed most modern 'damsels'! Lures have been around for years, the old Vivas, baby dolls, muddlers Jersey Herds etc are all, imo, lures which a fish takes more out of curiosity or agression than a pure feeding response.