Types of Dangerous Spiders. Arachnophobia, the fear of spiders, affects the psyches of many people to some degree, and the mere glimpse of a spider can send even the biggest individuals scrambling across the room. While most spiders are harmless to humans, several species do possess venom that can cause serious damage to a person if bitten. Of the world's five deadliest spiders, only two species, the black widow and brown recluse, are indigenous to the United States.
