THE DIAMOND-BACK TERRAPIN. I I I 



be obtained, but not always, from broods in which there are 5 to 12 males per 100 females. 

 However, when egg production is substantially increased it appears that there must be 

 more males to obtain maximum fertility. Broods in which the males numbered 24 to 

 32, respectively, per 100 females produced a normal fertility, even though egg production 

 was large. It seems warranted, then, to conclude that from 24 to 32 males per 100 

 females are necessary in order to obtain a 90 per cent fertility when the females of a 

 brood average perhaps from 12 to 24 eggs per season. Males are apparently a year 

 slower than the females of the same brood in coming to sexual maturity. 



The growth of terrapins from birth to their maturity is recorded. The increasing 

 number and percentage of individuals of a given brood reaching the 5 and 6 inch lengths, 

 the marketable size of terrapins, as age increases has been pointed out. In the sixth 

 year 60 per cent of a given winter-fed lot reached the 5-inch length and 6 per cent the 

 6-inch length. In the seventh year of a given hibernated lot 57 per cent of the brood 

 reached the 5-inch length and 1 per cent the 6-inch length. 



A large number of each brood of winter-fed terrapins will have reached the 5-inch 

 length by the fourth year. In the fifth year the average winter-fed terrapin will pass the 

 5-inch mark. Winter feeding not only hastens growth but quickens development of 

 the sex organs and influences toward greater fecundity at an earlier date than occurs 

 among terrapins allowed to hibernate. Offspring of domestic terrapins appear to do as 

 well in captivity as the offspring of " wild " stock. The maximum growth for any terra- 

 pin raised in captivity under observation has been 81 mm. for one year's and 104 mm. 

 for two years' development. Small terrapins seem to make faster growth when fed 

 oysters than they do when fed salt or fresh fish. Adults make good growth when fed 

 fresh fish. 



Selection of brood stock should not occur before the third year, preferably later. 

 Selection for this purpose should be of the largest individuals of a brood, since there is a 

 positive correlation between size, age, and fecundity. Earlier selection than in the third 

 year is undesirable, since rapid-growing 1 and 2 year old terrapins often have their 

 growth retarded in the following years and at the fifth year are no larger and no more 

 productive than those terrapins which were poorly grown in the first two years. 



It appears that the more space allowed terrapins in captivity the greater will be 

 their growth within certain limits. Plenty of space may also have a bearing in its possi- 

 ble influence on increased egg production. 



Mortality among yearling terrapins fed in a warmed nursery house during the winter 

 varied from 7 to 29 per cent from 1912 to 1919. Mortality among the adult terrapins, 

 as has been pointed out in another publication, is about one-half of 1 per cent. There is 

 no doubt that many more than one-half of the young terrapins of any brood will live 

 in captivity to attain a salable size. Yearling Texas and Carolina terrapins and the 

 hybrids of these stocks seem to be equally susceptible to a disease, probably bacterial, 

 which has killed many young terrapins in the nursery house at Beaufort. Disinfecting 

 treatments of the nursery house and boxes have not proved to be a consistent control 

 of the disease. 



