Probably the world’s most famous Arachnophobe is Little Miss Muffet. Confronted with peril, she takes the obvious course of action and beats a retreat.
Realistically, Ms. Muffet is not endangered, but how is she to be sure? Right; she isn’t. Why wait on events to find out? There are many situations in the Wild where Instinct trumps Reason, and a good thing too.
And don’t forget, Ms. Muffet abandons her breakfast. A sure sign of hysteria.