Besides my very own website-spammer dnsbl, I've just started a "spider-dnsbl" based on the data at iplists.com.
It lists mostly all IPs of the following spiders:
- googlebot - [127.0.0.2]
- inktomibot (yahoo) - [127.0.0.3]
- lycos - [127.0.0.4]
- infoseek - [127.0.0.5]
- altavista - [127.0.0.6]
- excite - [127.0.0.7]
- northern light - [127.0.0.8]
- misc - [127.0.0.9]
It's updated twice a day and can be queried via: spider.dnsbl.kennmer.net
~# host 188.8.131.52.spider.dnsbl.kennmer.net
184.108.40.206.spider.dnsbl.kennmer.net A 127.0.0.8
So this IP belongs to "northern light"...