Old foodie tradition dictates only eating wild oysters during months containing which letter?

Oyster is the common name for a number of different families of salt-water bivalve molluscs that live in marine or brackish habitats. In some species, the valves are highly calcified, and many are somewhat irregular in shape.

Some types of oysters are commonly consumed cooked or raw, and in some locales are regarded as a delicacy. Some types of pearl oysters are harvested for the pearl produced within the mantle.

Middens testify to the prehistoric importance of oysters as food, with some middens in New South Wales, Australia, dated at ten thousand years. They have been cultivated in Japan from at least 2000 BC. In the United Kingdom, the town of Whitstable is noted for oyster farming from beds on the Kentish Flats that have been used since Roman times. In the early 19th century, oysters were cheap and mainly eaten by the working class.

It was once assumed that oysters were only safe to eat in months with the letter 'r' in their English and French names. This myth is based in truth, in that in the Northern Hemisphere, oysters are much more likely to spoil in the warmer months of May, June, July, and August. In recent years, pathogens such as Vibrio parahaemolyticus have caused outbreaks in several harvesting areas of the eastern United States during the summer months, lending further credence to this belief.