162 GENERAL ZOOLOGY 



The spider crab (Libin'ia emargina'ta, frontispiece) stalks 

 slowly over the sea bottom in shallow and deep water where 

 rocks and fixed plants and animals abound. It can neither 

 run nor swim, an inference which might be drawn from the 

 slender, stilt-like appearance of its legs. Having no means 

 of aggressive defense, it relies almost wholly on the fact that 

 its color is very much like its surroundings. The cephalo- 

 thorax is covered with coarse, hair-like, flexible spines, and 

 the general color is dull gray. Frequently we find on the 

 back small seaweeds, hydroids (p. 271), sea anemones 

 (p. 275), and even rock barnacles (p. 166), growing as they 

 would on rock. This protective resemblance appears to be 

 very successful from the point of view of the spider crab, 

 for it is in some regions more abundant than any other 

 kind of crab. In some parts of Long Island Sound the 

 spider crabs are so numerous that they get into the lobster 

 pots set by fishermen and crowd them so that no induce- 

 ment remains for the lobsters to enter, much to the disgust 

 of the fishermen. Along the Atlantic coast this species 

 grows to have chelipeds which extend over one foot from 

 tip to tip. The giant Japanese spider crab has chelipeds 

 which extend over fifteen feet from tip to tip, and has a 

 body correspondingly large. 



The edible crab, more frequently called by naturalists the 

 blue crab (Callinec'tes sap'idus, Fig. 87), is characterized by 

 having sharp lateral spines of large size, and by the last pair 

 of thoracic appendages being flattened and adapted to 

 swimming. The chelipeds are strong and fitted for cutting ; 

 the succeeding three pairs of appendages have no nippers, 

 but come to a point. 



As is well known, the blue crab is caught in large num- 

 bers along the Atlantic and Gulf coasts for the markets in 

 the cities. The industry is of considerable value commer- 

 cially, and for that reason very general attention has been 



