Arachnophobia is a specific phobia brought about by the irrational fear of spiders and other arachnids such as scorpions. People with arachnophobia tend to feel uneasy in any area they believe could harbor spiders or that has visible signs of their presence, such as webs. If arachnophobes see a spider, they may not enter the general vicinity until they have overcome the panic attack that is often associated with their phobia.

Source: Wikipedia