212 CRUSTACEA. 



The Beckoning Crabs (Gelasimus)* have one of the claws, some- 

 times the right, sometimes the left, much larger than the other, and 

 the pincers of the smaller forceps shaped like a spoon. These 



FlG. 162. THIRD STAGE OF SHORE CRAB. 



creatures live in burrows, which they excavate upon the sea-shore, 

 and close the entrance by means of their large claw, the dispropor- 

 tionate size of which is thus found to be a wonderful and beautiful 

 adaptation to their habits. Their burrows are cylindrical, and carried 

 obliquely into the ground to a very considerable depth. They are 

 met with in great numbers, placed close together, but are usually 

 inhabited each by a single individual. From these crabs having 

 the habit of flourishing their large claw as if they were beckoning 

 to some one at a distance, they have received the name of " Calling 

 Crabs" (Cancer vocans). They pass the winter in their burrows, 

 without stirring abroad, and only visit the sea to lay their eggs. 



The Cocoa-nut Crab (Birgus) is said to climb the cocoa-nut 

 palms for the sake of procuring their fruit ; but Mr. Darwin says that 

 it merely lives upon those that have fallen upon the ground. Its 

 front pair of legs is terminated by very strong and heavy pincers, 

 the last pair by forceps which are narrow, and of a weaker structure. 

 After having selected a nut fit for its dinner, the crab begins its 

 operations by tearing off the husk, fibre by fibre, from that end where 

 the three holes are situated ; it then hammers upon one of them with 

 its heavy claws, until an opening is made, through which, by means 

 of its hinder pincers, it extracts the white, albuminous substance of 

 the nut. It inhabits deep burrows, where it accumulates sur- 

 prising quantities of picked cocoa-nut husks, on which it rests as on 

 a bed. Its habits are diurnal, but every night it is said to pay a 

 visit to the sea for the purpose of moistening its branchiae. It is 

 very good to eat, and the fat accumulated under the tail of the 

 larger ones sometimes yields a quart of oil. 



Dr. Gardner, in his " Travels in Brazil," says that while he was 

 near Rio San Francisco, he amused himself with watching the 

 operations of a small species belonging to the genus Gelasimus, that 

 was either making or enlarging its burrow in the sand. About once 

 in every two minutes it came up to the surface with a quantity of 

 sand enclosed in its left claw, which, by a sudden jerk, it ejected to 

 a distance of about six inches, always taking care to vary the direc- 



o), gelao, to laugh at or ridicule. 



