Need clarification on "Robots" hits in Google Analytics

I work for the U.S. Geological Survey and for years we've been using "Analog" to compile usage logs of web sites. A while back we added a 2nd report, where we tried to filter out "hits" from Robots. Often the non-robot reports showed only 30% of the hits of the full reports. Of course, these non-robot report were much more indicative of human usage, to me.

We are trying to get a definitive answer if Google Analytics displays hits from robots or not. The option we're using right now is to apply a Custom Segment of "Time on site > 1 second". But no one told us if "users" of < 1 second are the robots.

Can anyone clue us in on
(1) Google Analytics shows/does not show hits coming from search engine robots?
(2) Is using a Time<1 second the right way to filter out Robot hits?

Thanks a lot
Howard Perlman, USGS
hperlman@usgs.gov