Arachnophobia.

Recent studies of spider phobia have indicated that fear of spiders is closely associated with the disease-avoidance response of disgust.

It is argued that the disgust-relevant status of the spider resulted from its association with disease and illness in European cultures.

The "Disgusting" Spider : The Role of Disease and illness in the Perpetuation of Fear of Spiders; Graham C. L. Davey ; The City University, London