yahoo User_Agent and spider name?
 

what is the yahoo HTTP_USER_AGENT name?
also the spiders/bots from yahoo have any referers? (HTTP_REFERER is null or not?)

http://216.239.57.104/search?q=cache...&hl=en&start=1

Here is a list of a ton of crawler names, search for Yahoo.

Dunno about referrer names, but most/all decent crawlers identify themselves these days.