ARTHROPOD A 



169 



The Decapoda may be separated into two groups, the firsl 

 including animals like the lobster in which the abdomen is 

 strongly developed, and the second the crabs, in which the 

 abdomen is very much reduced in size. The lobsters are marine 

 Crustacea found in shallow water along the coasts ol Europe 

 and North America and are so extensively taken for food that 

 there is danger of their extermination ; from twenty to thirty 

 million are said to be caught annually on the coasts of New 

 England and Can- 

 ada. A trap called 

 a lobster-pot is used 

 for taking them, — 

 a semi-cylindrical 

 structure of slats, 

 which is baited with 

 some decaying ani- 

 mal matter, as this 

 forms the chief 

 food of the lobster. 

 When alive the 

 animal is usually 

 dark green in color 

 and becomes red 

 on boiling. 



The lobster-like 

 animals include the 

 fresh and salt wa- 

 ter crayfishes ( Fig. 

 160), the prawns _ 



Fig. 162. Pagurus bernhardus, the hermit 

 (Fig. l6l ), which cA, chela of first right leg; I.4, I.5, fourth and fifth legs ; t,ab- 

 havp a soft «hpl1 dominal terga; up, uropod. Aftei Bell, from Parker and 



' Haswell's Manual.) 



not calcified and 



with appendages for swimming instead of walking, the shrimps 

 (Fig. 161) and the hermit crabs (Fig. 162), which live in the 

 empty shells of snails. In these hermit crabs the abdomen is 

 soft and has lost nearly all of its appendages, as they would be 

 useless inside the snail shell, and the hard parts are confined 

 to the cephalothorax ; as the animal increases in size it seek 

 lareer shell. 



