Search Engine Spidering

How can i Know that a search engine came and spidered my website last night??

Thats very easy, just look in to your webite stats and you can find the name of spiders or bots in your stats.

Like if you see in your Webstat that a robot or spider named "Googlebot" visiting certain pages of your website than it means that google is spidering your website or if you see a robot/spider name as "scooter" than it means that search engine altavista is spidering your pages.