Pfui - 3:50 am on Sep 20, 2011 (gmt 0)
Apropos of I dunno what, 'plain' Slurp just cruised through and logged six same-dir index page referrers (out of 20 files hit throughout the day).
I don't recall any Yahoo bot EVER using (or appearing to use) referrers.
Mozilla/5.0 (compatible; Yahoo! Slurp; http://help.yahoo.com/help/us/ysearch/slurp)