A fear of death or a large natural predator is understandable. After all it is fear that has kept us alive for so long as the world developed and we developed along with it. Some of those fears are remnants of thousands of years of survival that is so ingrained in us that we can't shake it.
Take arachnophobia for example. I don't like spiders. I don't want them crawling on me or near me. I am disturbed when I see one and it vanishes. I would say my fear of spiders is moderate. My husband on the other hand is absolutely terrified of spiders. If one is spotted near him, he will not rest until it has been disposed of. He has used everything from shoes to lighters to put an end to the reign of any eight legged menace that dares enter his territory (aka: his visual range).
At times the fear almost seems irrational. To step back and take an objective look would make anyone with a fear of spiders appear as though they have lost their mind. The creature is a mere fraction of our size and weight. We can easily crush them under a boot heel. Most of the time they are just hanging out on a web or wall, not really hurting anything except the pests caught in their trap. In most places, the spider is not big enough to bring significant harm to a human being. Not to mention the many spiders that are probably lurking in the walls or hidden places in the average home on a daily basis that never do anything to harm us.
Yet many of us still fear the spider as though it was a killer waiting for us to turn our backs so it can creep up our pant legs and get at our throats. The emotion isn't purely learned, either. Our ancestors feared poisonous spiders, and with good reason. My husband and I here in Pennsylvania really have no significant poisonous spider population to worry about, yet we still experience the same unsettling fear.
It is both a physical and mental reaction. Thinking about it makes us nervous, but the fear also causes skin to crawl. My husband often complains of feeling itchy, as if things are creeping up his arms. It's mostly paranoia, but it is still interesting to see how that tiny little arachnid could cause such a powerful reaction that has a real physical impact.
Even looking at it from this perspective, I still would rather not have a spider crawling on me no matter how small it is. And I probably won't be visiting Brazil anytime soon.