When stomping around the jungles of Guam, you need to watch out for these guys:
I believe these spiders all come from the argiope appensa family:
http://en.wikipedia.org/wiki/Argiope_appensa
More commonly called garden spiders, these things weave huge webs and grow quite large, often with a body that is larger than an inch (three inches including legs). They are completely harmless, however the big ones still startle me, especially when I walk into a web by accident. The other day, I rode my mountain bike into a huge web by accident. While trying to get the strands out of my face, I saw one of these guys, a big one, crawling on my handlebars toward my left hand. I bailed off the bike quickly!
Supposedly, they are all over Guam because the local bird population, their primary predator, has been decimated by the brown tree snake.