DIAMOND-BACK TERRAPIN CULTURE 
57 
and the hibernating lot a gain of 8.9 millimeters during the 6 years prior to the last 
measurements, that is, between the ages of 8 and 14 years. 
The data presented in the foregoing paragraphs are illustrative of the extremely 
slow growth that is made by terrapins that are 8 to 10 years or more of age, and they 
suggest, as already indicated, that some females will never reach a length of 6 inches 
and that a small percentage may not even reach 5^ inches. It appears to be of 
interest to note that among the original wild brood stock confined, part since 1909 and 
part since 1911, and with few exceptions “adult” terrapins when secured, 17 females 
were under 6 inches in length when last measured (1925). It would seem almost certain 
that such animals will never reach a length of 6 inches. It is not surprising, therefore, 
that all females grown in captivity apparently do not reach a length as great as 6 
inches. In commercial terrapin growing it probably would not be profitable to retain 
the animals after comparatively rapid growth ceases; that is, after an age of 8 to 10 
Figure 13.— Rate of growth of a selected lot of the 
brood of 1921 
Figure 14.— Rate of growth of the brood of 1922. Line D 
represents offspring of domestic and line W of wild 
stock 
years is reached. A considerable percentage of the terrapins at these ages, as shown 
by the accompanying tables, are 5 inches and over in length and would bring a fair 
price on the market, and it seems doubtful if the increment in size thereafter would 
justify the expense of food and labor involved to produce it. 
The largest size attained to date by any terrapin grown in captivity is 6% inches. 
It is well known, of course, that in nature individuals measuring 7 inches and over 
in length occasionally are taken. A single female occurs among the wild brood stock 
confined at this station having a length of slightly less than 1 }{ inches (185 milli- 
meters). This animal probably approaches the maximum size attained by Carolina 
terrapins. The Texas terrapins, of course, grow somewhat larger and occasionally 
slightly exceed a length of 8 inches. 
Information relative to the rate of growth of terrapins in nature virtually is 
wanting. A few animals hatched at this station and liberated at about 1 year 
