these are the "spiders" that "crawl" websites... basically, the algorithms behind the search engines... Slurp is one of many... there is
Yahoo Slurp
Googlebot
MSNBot-media
MSNBot
Alexa (IA Archiver)
Internet Shinchakubin
Scooter
ZyBorg
Askbot
WebCollage
Voila
at my last job, we always disabled these as it always slowed down our sites since it kills bandwith