IT BEGAN AS A SCAM. SEVERAL CRATES, ALL INNOcently marked "Reptiles," were flown from Lagos, Nigeria, to the U.S. Their secret cargo: 1,000 Giant African Snails, considered by experts to be the most dangerous land snail in the world. By the time authorities knew they were in the country, the gastropods had slipped out to animal dealers in 25 states from Florida to Montana.
The baseball-size pets sell for about $10. To the right owner they provide sensitive, undemanding companionship. But if any of the Giant Africans are the same species that terrorized Florida for several years during the 1970s, they...