My poor mutt
doesn't seem remotely concerned about spiders but other animals that we find when we're out for a walk are a source of something to her. The something can range from:

Fear (noisier dogs)
Play (similar sized dogs)
Confusion (birds - she chases after pigeons and when they fly away her reaction is to come up to me with a look in her eye along the lines of "OK - how the hell did they do that?!")
Invitation (cats - wanting to play, or she did until a cat took a swipe at her a couple of weeks ago)

She's almost an analogue for me in the way in which she's an idiot, I regularly and with great affection refer to her "duty brain cell".
(Eds Meds Mathskillz=1,Socialskillz=0, Wed 10 Jun 2009, 11:13, Reply)