The handsome shell of the tiger cowrie, Cypraea 

 tigris, is concealed by the enveloping mantle as the 

 animal creeps along (left), but its spots show dis- 

 tinctly when the snail pulls back into its shelter 

 (right). (Berlin Aquarium. Otto Croy) 



Among the most wide-ranging land snails is the tiny 

 (shell Vi inch long) Lamellaxis (Opeas) gracilis, 

 carried bv commerce over the whole tropical world 

 from a probable origin in America. In the United 

 States it is found from South Carolina to Louisiana 

 and in greenhouses. (Japan. Y. Fukuhara) 



Together, these enemies of Achatina keep it in check. 



In 1847 a shell collector who visited Mauritius 

 took a few live specimens of A . fidica to Calcutta and 

 released them in the Chouringhie Gardens just out- 

 side the city. There the snails had no obvious ene- 

 mies, and the people — although often starving — re- 

 fused to touch them as food. The snails multiplied 

 and spread. By 1900 A. fiilicci had reached Ceylon 

 and had become a serious agricultural pest. By 1911 

 it was common around Singapore and, with further 

 human help, it island-hopped to Borneo. There, two 

 decades later, a bounty was offered for the bodies 

 and eggs of the snails, with no effect on their num- 

 bers. By 1933 Achatina was attacking rubber trees 

 on Sumatra and Java. In that year too it reached 

 Formosa, and was welcomed by the Japanese peo- 

 ple on the island as an interesting food and potent 

 medicine, although on no scientific basis. Living 

 specimens were shipped promptly to Japan, and by 

 1936 some had been carried by Japanese people to 

 Hawaii, where Achatina was soon out of control. 



The Japanese took A. fiilica to most of the islands 

 of the South Pacific, either just before or during 

 World War II. There the snails are providing more 

 lasting devastation than all the bombs and artillery 

 shells. They are still threatening to establish a beach- 

 head on the North American continent, and they re- 

 main a potential pest perhaps as menacing as most 

 of the fungus diseases or insect immigrants to reach 

 the western hemisphere. 



The Clams 



(Class Pelecypoda) 



One has only to mention clams, mussels, oysters, 

 and scallops to realize how many bivalves man en- 

 joys as food. If pearls are thrown in for good measure, 

 the economic importance of the class Pelecypoda 

 soars still higher. All of these creatures have a way of 

 life geared to the ultimate in retirement — existence 

 between two half shells in the seas or fresh waters, 

 depending upon food particles that can be drawn in 

 between the valves. 



The fact that clams and their kin cannot be active 

 on land and cannot fly is no reason to assume that 

 their habits are completely monotonous. Various 

 members of the class can leap or swim, tether them- 

 selves like captive balloons and then take off again, 

 cement one shell to the bottom and lie indolently ever 

 after, burrow many feet below the surface of the 

 ocean floor, cut cavities in rock and timber, plow a 

 furrow without getting stuck in the mud, creep up a 

 plant stem, or lie back in the tropical sun and raise 

 plants as food. Clams and their kin live in the great- 

 est depths of the ocean, and also in the shallow 

 waters at the source of every great river in the 



