of 130,070 drills, of which 1,6% were Eupleuia . Stauber (1943) ; also in Delaware 

 Bay. during 6 years of collecting noted the remarkable range of 0.03 to 35,50% 

 Eupleura from station to station In all cases but one his figures are based on 

 annual catches of both species in excess of 10, 000 and as high as 380. 000 . Over 

 a period of years in which more than two million drills were taken, only 3 .5% 

 were Eupleura . Thus it is difficult to conclude, as did Haskin (1935) that the 

 overall ratio of Eupleura to Urosalpmx is rapidly increasing on New Jersey oyster 

 beds It is possible nonetheless that in certain favorable areas the proportion of 

 Eupleura is increasing When Loosanoff (pers. com.), for example, started bis 

 researches in Connecticut in 1932 Eupleura was a rarity there; now in some areas 

 in Long Island Sound he finds it as abundant, or more abundant, than Urosalpmx, 

 And Andrews (pers. com,) in weekly collections of drills captured with baited 

 di ill tr a p S on Wormleys Rock. York River, Virginia, finds in a total of 6, 736 

 Urosalpmx and Eupleura collected during three summers in the last 12 years that 

 the percentage of Eupleura increased as follows: 1942, 29.3%; 1948, 23.5%; and 

 1952, 82.0% In Bo gue Sound, North Carolina, in the vicinity of the Institute of 

 Fisheries Research pier. Chestnut (pers. com.) in a general collection of 151 drills 

 found only one Eupleura ; and a collection in New River, North Carolina, of 23 drills 

 contained two Eupleura 



T. C. Nelson (1922) in a study of the comparative destructiveness of 

 Urosalpmx and Eupleura showed that when confined individually in cages with 

 oysters, Eupleura destroyed slightly more oysters than did Urosalpmx . Haskin 

 (1935) and Gaitsoff et al. (1937) state that the two species of drills are about 

 equally destructive; and the latter point out that Urosalpmx because of its much 

 greater abundance is the more serious pest of the two species. 



Haskin (1935) demonstrated that Eupleura is more active than Urosalpmx 

 in egg deposi'ion, laying an average of approximately 22 eggs per case, and a 

 range oi 8 io 42 eggs per case (based on a collection of 445 egg cases) in Barnegat 

 Bay New Jersey. Stauber (1943) noticed parallel fluctuations m the total number 

 oJ ^gg cases of both species collected on drill traps throughout the season, High 

 numbers of Eupleura egg cases were observed during the summer of 1937, and 

 relatively lower concentrations were seen during the subsequer t three summers . 



Haskin (1935) first described a hinged cap on the egg case o f Eupleura 

 analagous to that on the Urosalpmx egg case through which the young drills escape 



Stauber (1943) without experimental evidence suggests that the two drills 

 may possess similar minimum salinity death. times, 



From preliminary field observations Loosanoff (pers , com.) is led to be- 

 lieve that Eupleura is better adapted to life on soft muddy bottom than Urosalpmx 



102 



