When a strange story broke about the confiscation of a bag of giant African snails at JFK airport this week, I knew Patricia Highsmith was calling. The man who brought them from Ghana declared them to customs, but didn’t realise they were illegal. Why’s that, you say? ‘They eat almost anything, breed like crazy, and carry a terrifying parasite that causes something called “rat lungworm.” The snails can reach up to 8 inches long and 5 inches wide when fully grown.’

Most people do not see snails as cuddly pets, but then most people are not Patricia Highsmith. She famously smuggled them in her bra on trips between France and Britain because she could not bear to leave any behind. Vic Van Allen, the protagonist of her serial killer novelDeep Water(1957) adored his snails Hortense and Edgar and watched with sentimental rapture as they made love. That snail…