620 U. S. BUREAU OF FISHERIES 
Necessity is the mother of invention. Similarly, many other things that are 
not inventions are learned when necessity knocks at the door. Last summer 
we were handicapped for suitable out-door space for young terrapins that had 
hibernated. It was decided finally to place them in the hothouse temporarily, 
as that place was vacant, the animais that had occupied it having been liber- 
ated. It was known, however, that the extreme heat from the glass roof would 
kill them unless some protection were provided. This was accomplished by 
eoating the glass heavily with lime and by placing a board lengthwise over 
each tank, providing at least some shade at all times. This situation proved 
so successful that the animals were left there until they had to be taken out 
to make space for a new brood. Better growth than usual resulted, and the 
death rate was considerably lower. It is planned to repeat the experiment. 
I have already stated that time is no item in the life of a terrapin. Therefore 
the year’s growth gained by feeding the young the first winter probably is of 
no great importance when the animals are to be liberated. In practical terra- 
pin farming this is of value, as the turn-over is shortened. The house that we 
have at Beaufort is large enough only for experimental purposes. At the 
present time we have crowded the animais very closely in some of the tanks 
and are holding as many as 100 to 125 in compartments scarcely 2 feet square. 
This is much closer crowding than has even been thought permissible. It is 
too early to know what the result will be. I can say only that so far the 
crowded animals appear to be getting along just as well as the less crowded ones. 
Under the largely ‘“ overcrowded” conditions, space was found for only about 
2,500 animals. This number, within a few years, wiil be only as a drop ina 
bucket when compared with the large number of young that will be hatched. 
I am not prepared, at this time, to reeommend the construction of a larger house, 
because I have not had time to study carefully all the data on hand relative to 
the difference in the death rate among the winter-fed animals, as compared — 
with the hibernating stock. Deaths undoubtedly are fewer among the winter- 
fed animals, but how great the difference is can be determined only after an 
analysis of the extensive data is completed. This is what I regard as important, 
rather than the year’s growth gained through winter feeding. 
All the resu-ts concerning winter feeding through the years 1911 to 1925 are 
clouded by one factor—namely, heat. During all these years the house has 
‘been heated by means of a stove. It is utterly impossible to supply uniform 
and even heat all over the house at all times with a stove. Almost invariably, 
and largely without regard to the treatment given or the kind of food supplied, 
the greatest amount of growth has taken pace among the terrapins nearest 
the stove, and the least growth has occurred in those farthest removed from 
the heat. This appears to show that a uniformly high temperature is highly 
desirable. The diamond-back is a cold-blooded animal, and without doubt diges- 
tion stops when the body temperature falls below a certain degree, as has been 
shown, experimentally, to be the case in a fresh-water relative. When diges- 
tion stops, it follows that growth also ceases. The interpretation of the results 
of virtually all of the many experiments performed in winter feeding is difficult, 
as it is impossible to know how much to charge to the important factor—heat— 
and how much to the treatment given, food supplied, and to other factors. A 
better heating plant is absolutely essential for the conduct of further experi- 
mental work in winter feeding. 
Very extensive data on diamond-back terrapin culture that have not been 
ana:yzed properly have been accumulated at Beaufort. The working up of 
these data is the job immediately in hand. 
FISH IN RELATION TO MOSQUITO CONTROL 
We have heard much about the use of fish during the past few days. One 
important use has not been mentioned, however. I am referring to the em- 
ployment of fish for the control of mosquito breeding. I am thoroughly con- 
vinced that fish are so important in this connection that many regions now 
occupied by man would be entirely uninhabitable were it not for the degree 
of mosquito control provided by fish. Such prosperous cities as Wilmington, 
N. C., and Savannah, Ga., for example, would never have been built had it 
not been for the measure of mosquito control provided by fish, I am as sure 
of that as I am of anything. Yet when fish are spoken of, few people think 
of these animals in that connection. In fact, it is only very recently that the 
value of fish as agents for mosquito control has been known. How unusual 
it is to think of fish in this connection I can best illustrate by telling you of a 
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