114 BULLETIN OF THE BUREAU OF FISHERIES. 
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 undisturbed, 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 shell or assisting the movement by slow sculling strokes. In such cases 
the movement is in any direction—forward, backward, or sidewise—although the usual direction is 
sidewise. If the animal becomes alarmed, it moves away by a combination of the walking and swim- 
ming motions and often disappears like a flash. * * * All the legs are in motion except the large 
first pair. Of the latter, the one on the side toward which the animal is moving is held straight out 
sidewise, while the other is folded up under the shell. 
The coloration of the crab is such as to harmonize very perfectly with the surroundings, and the 
animal attempts very little concealment if there are other objects on the bottom. Often, however, 
a clear, sandy bottom or some oozy pond will be found to be almost alive with crabs which have buried 
themselves until only their eyes and their antenne are exposed. 
The experience of the present author has been that it is only immature crabs 
which bury in this manner. No adults were found so hidden. 
In thus hiding, the crab goes nearly vertically backward into the bottom and then, by a few 
movements, turns slightly, so that the shell rests at an angle of about 45 degrees. The material above 
settles down and effaces all traces of the entrance. It usually happens that the bottom affected by the 
crab is firm enough to render this operation somewhat slow and it rarely attempts to escape pursuit 
in such a way. It seems probable that concealment is usually adopted as an ambush from which a 
sudden attack can be made on some passing fish. 
The author has often seen immature crabs dart away and burrow in the sub- 
stratum, as described above, apparently in order to escape pursuit. It is probable 
that burrowing may be undertaken either for the purpose of escape or for lying in 
ambush. Hay describes an interesting habit of the crab which the author has never 
had the opportunity of witnessing: 
In certain places, notably shallow ponds and streams which become nearly dry at low tide, the 
crab may be observed to dig rather large, conical holes, apparently as reservoirs, and to take up its 
position in the deepest part * * * and waits until the rising tide offers an opportunity to move 
about again. 
The hole is described as about 1 foot across and 6 inches deep. The sand or mud is 
loosened by means of the tips of the walking legs and carried, clasped between the 
claw and the underside of the body, to the side of the excavation. 
The color of the crab is more or less variable, and it is believed by the fishermen that the animal is 
able to change its hue slightly to approximate the color of its surroundings. Light grayish-green in- 
dividuals are said to be taken on sandy bottoms, while the dark olive-green are said to be found among 
the grass. This theory, however, is not very well borne out by crabs held in captivity in the live boxes, 
for there they retain their original colors, and even after they have cast their shells exhibit quite as 
much variety as before. 
The author agrees with the last statement of Hay and is of the opinion that there 
is no approximation of the color of the bottom by the crabs. In a catch, all the indi- 
viduals of which were taken from the same area, he has seen specimens exhibiting all 
the varieties of colors which are found in crabs. 
The blue crab’s food is of a varied character, but the animal is preeminently a scavenger and a 
cannibal. In the shallow waters of ponds and small tidal streams it preys to a certain extent upon 
small fish, which it stalks with some cunning and seizes by a quick movement of its large claws. In 
such situations, too, I have sometimes observed it nibbling at the tender shoots of eel grass or other 
aquatic vegetation, or picking at the decayed wood of some sunken log. Its favorite food, however, 
is the flesh of some dead and putrid animal, * * * stale meat ora rotten fish. 
