What is the fear of spiders called?

Arachnophobia, and it is among the most common specific phobias - surveys put some degree of it in a large minority of people, with a marked skew towards women in most Western samples. Whether that is innate or learned is a real argument: infants show heightened attention to spider shapes before they could have learned to fear them, which suggests a prepared bias rather than a taught one.

The evolutionary explanation is popular and shakier than it sounds. Very few spiders anywhere are dangerous to humans, and in Europe essentially none - so a hardwired fear of spiders would be a poor investment compared with, say, a fear of heights or of snakes, which killed a great many more ancestors. One alternative is that spiders were associated with disease and contamination in medieval Europe, which would make it cultural and would explain why the fear is much weaker in regions where spiders are eaten.

It is also one of the most treatable conditions in psychiatry. Exposure therapy has an unusually high success rate, and single-session treatments lasting two or three hours have taken people from unable to enter a room with a spider in it to holding one, with the effect persisting for years. Virtual reality versions work too, which is a strange thing to be true of a fear.