Can I tell spiders to only come at night? Sounds like a dumb quesiton but I have lots of pages and slurp seems to use lots of bandwidth. The other robots seem to use less.
be happy to have spiders that means you also may get (some) traffic their day might be your night and vv hence you may tell themn anything you love - but spiders have no need to listen to what you tell except robots.txt http://www.robotstxt.org/
No really can't tell spiders to come at night on your site. You cant controls spiders that are from different computers. only the admins of those computers with the spiders can control them. But its good thing to have them coming day and night to view your site. So i rather suggest just leave it be.
Do you anything special for them at night? I think that's the known issue faced by most of the high traffic site's webmasters. You are one of them! What kind of website is it? Is it a forum, ecommerce site, blog ....? I know there are some tweaks for forums to resolve on these issue - speed, bandwidth etc.
If they are particular pages or file types (images/pdfs etc) which you donot want to be indexed, you can block those for Slurp. Otherwise there is no option to limit bot to a specific hour of the day.
You could create a shell script to overwrite robots.txt with either allow or disallow all and run cron if you just had to block the robots during the day. The risk is, they might not come back at night... and remember, night is different in different parts of the world!
lol, if you are much concern about them and if they are making you bad feel, just block them forever using robots.txt file (Why to invite such unnecessary bots to eat up your bandwidth and overload your site.)