but to oysters one year old (see Table 8) and are taken (no citation given) from 

 Haskin's (1935) work in Cedar Creek, New Jersey. Cole (1942) estimates that in 

 England during a seasonal feeding period a drill feeding exclusively on one year 

 old oysters would destroy 59 spat, Stauber (1943) estimates that a medium sized 

 drill destroys approximately 20 one year old oysters per season. 



The rate of destruction of prey by (Jro salpinx depends, among other 

 possible factors, upon the size of the drill and of the prey, the temperature and 

 the salinity of the environmental water, and possibly the state in the reproductive 

 cycle of the drill The reported information on the influence of size of predator 

 and prey on the rate of predation is summarized in Tables 8 and 9. These figures 

 highlight the fact that as Urosalpinx increases in size it is capable of destroying 

 greater quantities of oysters of a given size (Newcombe, 1941=42; Engle, 1953), 

 and that a given size of drill can destroy a greater quantity of small oysters than 

 larger oysters (most of Table 8, more specifically Gole, 1942; Adams, 1947). 

 Stauber's (1943) figures seem to indicate that small drills destroy more seed oysters 

 than do large drills; however, seed oysters vary considerably in size, and it is not 

 known what size oysters were fed to the respective size groups of drills. 



That seasonal temperatures strongly influence the rate of destruction has 

 been reported by a number of investigators . Pope as early as 1910 stated that 

 drills consume little food during the cold months of the year. He encountered 

 considerable difficulty in attempting to induce drills to feed in the course of ex- 

 perimental observations after September in Massachusetts Galtsoff et al. (1937) 

 v/rite that during 9 weeks in a study (in Cedar Creek, New jersey; Haskin, 1935; 

 no citation given) the temperature of the water rose from 19.0 to a peak of 28.0°C 

 and dropped to 24. 9° C; during this time the average number of oysters destroyed 

 each week in experimental baskets at 10 different stations by a total of 200 drills 

 increased with the temperature from an average of five at the beginning to 8 

 during the weeks of high temperature and down to 6 at the end of the 9 weeks. 

 Engle (1940) working with drills in an outdoor tank in Connecticut noted that the 

 active feeding season lasted from late May to late November . The peak of feeding 

 occurred during the latter part of July and in August. Cole (1942) in a study of the 

 potential damage of_U. cinerea i n England confined drills with an excess of 

 oysters in cages in the field In a plot of the daily rate of destruction of one year 

 old English oysters and water temperature for the season of 1941, Cole demonstrates 

 strikingly that drills start feeding actively as the temperature of the water rises 

 above 14 D C, feed voraciously during the major part of the breeding season through 

 mid July, and then a fairly good general correlation occurs between water tempera- 

 ture and rate of feeding during which the feeding rate declines as water temperatures 

 drop During the active spawning period he obtained destruction rates as high as 

 6.30 oysters per drill per week, a rate considerably higher than the average figure 

 of 2 . 92 for the season (see Table 8) These data prompted Cole to warn against the 



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