conch, which attains a length of 6 inches, is 

 quite numerous on certain oyster beds of the 

 Atlantic coast. A conch opens an oyster by 

 pushing the edge of its own shell between the 

 oyster's valves. It then inserts its proboscis 

 between the shells and eats the meat. Some- 

 times conchs chip the edges of the mollusk's 

 shell until the proboscis can be inserted. In 

 southern waters Busycon contrarium , or light - 

 ning whelk, destroys many oysters, while 

 still another gastropod, the crown conch, 

 Melongena corona , also nnay kill oysters 

 although it is not considered a serious oyster 

 enemy, 



Predaceous snails can be controlled by 

 chlorinated benzenes, such as orthodichloro- 

 benzene, or a mixture of several such hydro- 

 carbons known under the commercial name of 

 Polystream. These chemicals are mixed with 

 dry sand, broken oyster shells, or other inert 

 material, such as clay, to carry them to the 

 bottom and keep them there. The effectiveness 

 of the treatnnent can be increased by incor- 

 porating in the chlorinated benzenes other 

 chemicals, such as Sevin, an insecticide rela- 

 tively nontoxic to mannmals. 



The treatment may consist of surrounding 

 the shellfish beds with a belt of chemically 

 treated sand, thus preventing entrance of 

 enemies, or the sand may be spread over an 



entire infested area, seriously affecting or 

 killing the drills and other undesirable gastro- 

 pods (fig. 13). Because certain snails, such 

 as the clam-killing snail, Polinices , are able 

 to move under several inches of bottom soil, 

 they may not be stopped by merely spreading 

 the chemically treated sand. However, an 

 effective three-dimensional barrier may be 

 created by injecting the chemicals or plugs of 

 treated sand into the bottom. 



The methods described above were found 

 quite effective when applied in nature. Studies 

 are being made to ascertain if the methodmay 

 be approved by the U.S. Public Health Service, 

 which is interested in all instances in which 

 chemicals come in contact with human food. 



Still another group of small marine snails, 

 belonging to the genus Odostomia , feeds on 

 oysters. These snails attach themselves to 

 the oyster body by an oral sucker, pierce the 

 body wall with an organ resembling a stylet, 

 and suck the oyster blood, perhaps also de- 

 vouring some solid tissue. 



The starfish, Asterias forbesi , found in 

 large numbers in New England, especially in 

 Long Island Sound, and sometimes in large 

 concentrations in the lower part of Chesa- 

 peake Bay, is another important oyster enemy 

 (fig. 14), It opens oysters by pulling the valves 

 apart with its tube feet. The starfish mouth is 



Figure 13. — Oyster conch, Busycon canaliculatum . in expanded condition caused by chemicals used for 



control of undesirable snails on oyster beds. 



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