Don't try this if you only want castration, it could lead to penectomy.

This is bad & sad: http://brown-recluse-spider.ascendedhea ... ctures.htm

Scroll down through the pictures until you see the ugly result.

Weirdly enough, recently my dad had to throw a spider out the window of his truck because it was trying to bite his crotch. He normally gets along well with spiders, but this one seemed to have interesting motives...