LIFE HISTORY OF THE BLUE CRAB. 401 
Within the larger bodies of water the crabs are quite generally dis- 
tributed—that is to say, individuals are not uncommon anywhere, but 
there are certain localities where their abundance is almost incredible 
and the supply seems inexhaustible. These favored spots seem to be 
the mud bottoms such as are to be found near the mouths of the larger 
rivers, in shallow water where there isan abundance of vegetation. 
Hard bottoms, oyster beds, or bottoms consisting of soft ooze without 
vegetation are apparently not best suited to their welfare, for on such 
spots comparatively few crabs are to be found. 
The habitat varies considerably with the season. In the summer 
the crabs live close to the shore; in the winter they move into deeper 
water. It would also seem that the habitat varies somewhat with the 
age and sex of the individuals, for even in the summer the small and 
medium sized crabs are most abundant in shallow water, while the 
large males remain in the deeper channels.¢ An examination of the 
crabs from shallow water shows that small males and virgin females 
constitute the buik of the catch. 
POWER OF MOVEMENT. 
Either in the water or on land the blue crab is an animal of great 
activity and has considerable power of endurance. Progression 
through the water is effected by means of a sculling motion of the 
broad, oar-like posterior legs, and under ordinary conditions is slow, 
the effort of the animal being apparently only to keep itself afloat 
while it is borne along by the current. Under these conditions the 
moyement is either backward or sidewise. The shell is held with the 
posterior portion uppermost, the legs are brought together above the 
back and strike backward and downward at the rate of from 20 to 40 
strokes per minute. When alarmed, however, the animal strikes out 
with great vigor and rapidity, moving its paddles too swiftly for the eye 
to follow; it moves through the water almost as rapidly as a fish and 
quickly sinks below the surface. When on the bottom and undis- 
turbed, the crab may be seen to walk slowly about on the tips of the 
second, third, and fourth pairs of legs, the large pincers being held 
either extended or folded close under the shell and the paddles either 
raised and resting against the back of the sheil or assisting the move- 
ment by slow sculling strokes. In such cases the movement is in any 
direction—forward, backward, or sidewise—although the usual direc- 
tion is sidewise. If the animal becomes alarmed it moves away by a 
combination of the walking and swimming motions and often disap- 
pears like a flash. In fact, so rapid is the movement that it is almost 
impossible to see how it is accomplished. It is too steady and uniform 
“This fact is well known to the fishermen, who frequently refer to these large males 
as ‘‘channellers.’’ 
F. C. 1904—26 
