Well, now we embark on the old wing debate. I guess if you are Royal Wulff, who we know CAN and DOES tie great wings, you are entitled to your opinion that wings don't matter. However, if you're a tier who doesn't like them because he can't tie them, that's another thing. It's hard for me to believe that a good way to imitate an insect that's MOSTLY wing is to leave them off, but one can argue that the trout don't ever see them from underneath. I don't really buy that myself, but one can argue that. I see all sorts of theories put forth all the time, including the one where a fly that doesn't look like anything at all is just the ticket. But go back to what it is we're trying to do here. Are we or are we not trying to imitate insects with our flies? Or in the case of impressionistic flies, imitate insect activity?
The reasons wings are split are aerodynamic. In addition, there are great numbers of mayflies whose wings are split, though many have them together as stated. I tied a fly for the Henry's Fork half spent because I saw so many PMDs with their wings like that. Banged 'em big time.
Eric