124 BULLETIN OF THE BUREAU OF FISHERIES. 
have given instances in which buoys were left to mark an area on which crabs were 
abundant, and on the next day it was found that the crabs had moved away. Other 
instances have been given in which dredgers systematically followed a school of crabs 
from one point to another. These facts show that the crabs may move about to a 
considerable extent during the winter months. 
From observations which were made on crabs being kept in floats, it was found 
that, as the temperature lowered, the crabs became more and more sluggish and at 
about 50° F. moved very little and practically ceased to eat. On warmer days they 
became more active. Crabs were also kept in wire crates partly sunk in the mud. 
At various times during the winter examination was made and it was found that the 
crabs had not buried in the mud. 
It seems most probable that the crabs, instead of burying, merely move toward 
deeper, and consequently warmer, water as winter approaches and as the temperature | 
falls become more and more inactive and finally lie motionless on the bottom. On 
milder days they move about to some extent, especially if disturbed. 
LENGTH OF LIFE. 
The only original statement concerning the length of life of the blue crab which is 
found in the literature is that of a correspondent quoted by Dr. Mary J. Rathbun.? 
The probable duration of the life of both the male and the female is there estimated to 
be seven years. The correspondent bases his conclusion partly on certain wholly casual 
observations made during his boyhood and partly upon assumption. The period before 
the crab attains maturity is stated to be three years, and it is thought to molt twice each 
year during this time. As the correspondent is dealing with the blue crab found near 
Victoria, Tex., it is possible that the life history of that form is widely different from that 
of the crab of the Chesapeake Bay, although both belong to the same species. On the 
whole, however, it does not seem that a great deal of weight can be attached to the 
opinions set forth on this subject by the correspondent. 
In connection with the blue crab of the Atlantic coast, and of Chesapeake Bay, 
in particular, experiments and observations led to a very different conclusion from that 
arrived at by the person mentioned by Dr. Rathbun. It was found that a crab which 
is hatched during one summer will reach maturity the next, molting from 15 to 20 times 
during this interval. It then mates and, in the case of the female, spawns at the age 
of 2 years, during the summer following the one in which mating occurs. The female 
was also found to be able to survive the winter following the first spawning and to 
spawn again at the age of 3 years. It is probable that this is the usual length of life 
of the female, although some may survive until yet another season. In the case of the 
male, there are no spawning periods by which to judge its term of life. The best 
evidence available shows that the males mature in one year, as do the females. During 
the spring and early summer full-sized males are found which, judging from their brown- 
ish color and the presence of barnacles, etc., upon their shells, have survived at least 
one winter after reaching maturity. It is very probable that the usual term of life of 
both the male and female crab is 3 years. 
@ Rathbun, on. cit., p. 370. 
