The bat is a symbol of good fortune because the word ‘bat’, biān fú (蝙蝠), is a play on the word ‘luck’, fú (福). A drawing of two bats facing each other represents ‘double luck’, shuāng fú (雙福). A red bat is an especially luck omen because red is believed to be the color that wards off evil and ‘red’ is pronounced the same as ‘vast’, hóng (洪). Together, a bat paired with a coin means ‘luck before your eyes’, fú zài yǎn qián (福在眼前). The bat is also associated with longevity because the ‘Book of Herbal Medicine’, written at the end of the sixteenth century, states that the bat lives to a great age and its blood, gall bladder, and wings have medicinal benefits for eyesight and long life.