I dont know but the spider has been to my site every day for last week. It only crawls specific pages (Pages with the word forum in the title, even thou i dont have an auctual forum).
Every visit it has a different IP address, and it runs the scans around the same time.
I believe it is for this search engine
http://www.a9.com/
as I am listed in it, but to be honest I have no idea.