An amusing column by Olivia Judson in Saturday’s Herald Tribune: She writes: "Since organisms that cause sexually transmitted diseases can only spread if those who are infected copulate with new partners, you might therefore expect they would evolve to enhance their host’s desire for new sexual encounters. Testing this in humans is problematic. But it could be looked at in other animals. Indeed, there is tentative evidence that insects are sometimes victims of such manipulation."

You believe you are sexually aroused, but it’s just your STD.