THE DIAMOND-BACK TERRAPIN. 



IOI 



If, however, one selects the largest grown three-quarters of each lot, the average growth 

 increment for i-year-olds is much increased. To indicate this point, a concrete example 

 will best serve the purpose. There were 1,004 terrapins of the 1916 hatch placed in 

 the nursery house in November, 19 16. During the following winter 500 or more of the 

 same brood were allowed to hibernate, while the larger lot was fed. In May, 19 17, 

 the average length of the 1,004 was 39- 2 mm - The best grown three-quarters, or 780 

 terrapins, had an average length of 42.9 mm. The largest 200 terrapins of this lot 

 averaged 54.7 mm. in length. To be compared with this lot there was still the un- 

 changed fall average measurement of the hibernated terrapins, 28.1 mm. 



From this discussion it appears that it would be economical to cull the young, 

 poorly grown terrapins, either to force-feed them, liberate them because of their relative 

 costliness in handling, or to sell them as soon as possible after they reach the 5-inch 

 length in order that all the fast-growing characteristics of the brood stock may remain 

 unmixed and protected against contamination with slow-growing individuals. 



Present knowledge of the relative growths of first-year "runts" and first-year 



"selects," however, indicates that discarding or too strict culling of "runts" at the end 



of the first year is not entirely economical, since it has been learned that terrapins of 



poor first-year growth often reach in the fourth or fifth year equal length with their 



"select" brothers. It would doubtless be profitable to destroy very early any yearlings 



that show symptoms of disease unless effective remedial and prophylactic treatments 



are available. 



WINTER FEEDING. 



In view of the fact that in some locations favorable for terrapin culture fresh food 

 may not always be available or may cost excessively, experiments have been carried 

 on to learn the relative value of fresh and salt food in its assimilability and its growth- 

 producing value. For this purpose one lot of newly hatched terrapins with an average 

 length of 28 mm., 662 in number, was fed oysters, while another lot of the same age 

 and average length, 613 in number, was fed salt fish. It appears from the following 

 tabulation that the fresh-fed terrapins thrive much better than the salt fed : 



The maximum length of any terrapin under our observation kept through one 

 winter and until the following May in the nursery house is 81 mm.* The greatest 

 length of a winter-fed terrapin at approximately 2 years of age (measured in September) 

 is 104 mm., or slightly more than 4 inches. The offspring of domestic stock appear 

 to do better in captivity than those of "wild" stock (fig. 78). From measurements 



• These measurements are taken on the lower shell, following the commercial method of measuring a terrapin: 81 

 mm. Oj'i inches ; 104 mm. O 4'i inches. 



