THE CRUSTACEANS 93 
the crab instantly withdraws within its shell, completely closing 
the opening with its claws, which are of the exact shape 
required for the purpose. 
As the crab grows it 
must occupy larger and 
larger shells. These are 
apparently selected with con- 
siderable care, but having 
decided upon it the crab 
finally darts into its new 
abode with almost incredible 
rapidity. In common with 
other crustaceans these crabs 
are scavengers. They are 

also inveterate fighters, and 
will conquer and devour one 
another when opportunity Fig. 60; HERMIT CRAB. From Life. Showing 
the borrowed shell covered with sea weeds 
offers. A number of marie and Hydractinia. Cape Ann, Mass. 
animals grow upon the shells, 
which are carried,about by hermit crabs, thus obtaining the advan- 
tages of a wandering life. Several species of hydroids, such as 
Hydractinia, cover the shells 
with soft, pink-white, velvety- 
looking growths, while a num- 
ber of sea anemones also live 
upon the shells. One of these 
called ( Epizoanthus america- 
nus) finally dissolves the shell, 
forming a cavity within which 
the crab continues to reside. 
One of the most interest- 
ing of the hermit crabs is the 
Robber Crab ( Birgus latro) of 
the tropical Pacific Islands. It 
is about two and a half feet 

Fig. 61; HERMIT CRAB. From Life. 
Bere nics long, and the abdomen is soft 
below but protected above by 
hard plates. It lives within deep burrows, and only occasionally 
visits the water. It crawls to the top of the cocoanut trees, and 
tears open the nuts for the sake of the white “meat.” 
