feed.rg occurs. Kellog (1901) reports some destruction in the field of young Mya 

 arenana , and Gibbs (pers. com.) in Palmer River, Rhode Island, and the writer 

 in Little Egg Harbor New Jersey encountered significant quantities of drilled young 

 hard ci ams ( Mercenaria (= Venus) mercenaria ) . 



The pionounced predilection of Urosalpinx for the younger stages of the 

 oyster has been emphasized repeatedly (Pope, 1910-11; J. R Nelson, 1931; 

 Federighi, 1931c; Galtsoff et al., 1937; Cole, 1942; Haskin, 1950), andwhe 

 oyster culture is practiced intensively the drill feeds almost exclusively on these 

 (Stauber. 1943), Pope and later workers write that when small oysters are placed 

 in the vicinity cf large oysters being attacked by drills, the drills invariably 

 desert the larger for the smaller prey 



A. rumber of observations suggest that under seme, although not ail, 

 conditions U rosalpinx feeds on the mussel Mytilus e dulls in preference to the 

 oyster Crassostrea vir ginica . Haskin (Galtsoff et al., 1937, , . from Haskm, 

 1935) during the course of experiments with individual drills in Cedar Creek, New 

 Jersey placed small Mytilus in two field cages with small oysters and drills In 

 one cage all four Mytilus were destroyed before any oysters were attacked, and 

 in the other cage only one oyster was drilled while three Mytilus were consumed 

 Further experiments in large scale trapping of drills in Delaware Bay in which 

 separate traps were baited with young oysters, young mussels, and empty shells, 

 demonstrated that mussels were twice as efficient in attracting drills as oysters. 

 Later (1950) in field cages and in the laboratory when Haskin confined mussels 

 (size not given) young oysters, and drills, he observed that in tlie field 3 6 and 

 in the laboratory 3, oysters were drilled for every mussel drilled. Cole (1942) 

 confined English drills with a number of food organisms in field cages and 

 observed that drills offered Ostrea edulis spat and Mytilus edulis destroyed 

 practically all the spat before attacking the mussels, which were then quickly 

 consumed. Barnacles were more attractive than mussels, and about equally 

 attractive as one year old oysters. 



Jr. feeding experiments in an aquarium Galtsoff et al. (1937) observed that 

 barnacles were readily attacked by drills and that penetration of the prey was 

 effected through the soft, parts between tne plates of the barnacle. They conclude 

 that dri'ls exhibit a decided preference for barnacles probably because of the 

 vulnerability of the prey. 



Under laboratory conditions Urosalpinx feed not only on animals which they 

 have drilled, but also on flesh removed from these animals (Federighi, 1931c) 

 Federigh; placed the excised tissues of freshly killed oysters (Cra ssostr ea), clams 

 (Mercenaria) , scallops ( Aequipecten ), oyster drills (Urosal pinx) . slipper limpets 

 ( Crepidula ), pin fish ^La godo n) ; spots ( Leiostomus ), and croakers ( Microp ogon) 



49 



