In the cages in English waters Cole (1942) noticed that drilling may begin 

 as soon as the temperature of the water exceeds 11-12° C and ceases when the 

 temperature descends below this limit, Engle (1953) found that at Annapolis, Mary- 

 land, the first drilling of oysters took place in temperatures ranging from 11 .6 to 

 17 ,4° C; in Long Island Sound, New York, it began after the water temperature 

 reached 11 ,6°C; and in Delaware Bay it commenced at 12°C and discontinued at 

 about 8°C In a review of FederighTs (1931c) data he notes that Federighi's drills 

 did not stop feeding until temperatures fell below 7.6°C. Andrews and McHugh 

 (pers. com,) at Gloucester Point. Virginia, observed that drills 5 to 17 mm. in 

 height drilled oyster spat m the period January 20 to March 10 at an average temper- 

 ature of 6.5° C during which the highest temperature recorded was 9.5 e C. Thus it 

 appears that Federighi's minimum temperature for feeding is probably too high. 

 Loosanoff and Davis (1950-51) using drills from various geographic regions in 

 laboratory experiments found that a few drills from Rhode Island, Long Island 

 Sound, New Jersey, and Virginia attempted to feed at 6° C; at 9° C a number of 

 these drills and a few of those from North and South Carolina fed (Table 14). 



Haskm (1935) in field studies in Barnegat Bay, New Jersey, in which 20 

 drills were caged With 15 one year old oysters in each cage at 13 different stations, 

 noticed that in the range observed, 19 to 28 C C, the rate of destruction of oysters 

 increased with the temperature . 



Oviposition 



The reported temperatures at which the drill begins to oviposit also vary 

 in different geographic regions but the postulated correlation with latitude (Table 13) 

 is not always clear. In both laboratory and field observations in Hampton Roads ; 

 Virginia, and in Beaufort, North Carolina, Federighi (1931c) found the first egg 

 cases after the temperature of the water had risen above 20° C for some time. In 

 Delaware Bay, New Jersey, according to Galtsoff et al. (1937) egg case deposition 

 begins after the temperature of the water has reached 13.9'C. Stauber (pers. com.), 

 however, seriously questions the accuracy of this observation; in drill trapping and 

 drill dredging operations in the same bay and confining drills in cages with oysters 

 over a period of 7 years, he (1943) found that in general no egg cases were laid at a 

 temperature lower than 15°C. During July as the water temperature approached 

 25° C oviposition diminished almost to zero and remained at this low level until 

 September when a period of water temperatures fluctuating from 25 to 15°C 

 initiated a second but minor spawning He notes that the spawning period of chills 

 in shoal areas will be advanced over that of those in deep water, whereas that of 

 drills in intertidal areas may either precede or lag behind deep water areas depend- 

 mg upon atmospheric conditions. Loosanoff (1953) in Long Island Sound has found 

 clusters of recently deposited Uro salpinx egg cases at depths of 30 feet at a minimum 



74 



