HERMIT-CRABS. 331 



The most plucky and pugnacious of these little crabs are those 

 which occupy cast-off Nerita shells, a character whicli probabty 

 arises from their consciousness of the solid strength of the home 

 they have chosen : and, strange to say, the tiny bosses on the 

 surfaces of the large pincers, which are outermost in the improvised 

 operculum, resemble similar markings on the outer side of the oper- 

 culum of the Nerita {N. marmorata, Hombr and Jacq), whose shell 

 they often inhabit. Mr. Darwin^ observed that the different species 

 of hermit-crabs, which he found on the Keeling Islands in the 

 Indian Ocean, used al\va3^s certain kind of shells ; but I could not 

 satisfy mvself that such was the case in the instance of the Solomon 

 Island hermit-crabs. In the case of the common beach species of 

 Coenobita, I found, after carefully examining a number of indi- 

 viduals to satisfy myself of their being of the same species, that 

 shells of the genera Turbo, Nerita, Strombiis, Natica, Distorsio. 

 Triincatella, Terebra, Melania, &c., &c., contained the same species 

 of Coenobita, whether the individual was large enough to occupy a 

 Turbo shell of the size of a walnut or sufficiently small to select the 

 tiny shell of the Tncncatella for its home. Another species of the 

 same genus prefers usually the vicinity of the beach ; but it may 

 occur at heights up to 200 feet above the sea. It is rather largei- 

 than the beach species, and differs amongst other characters in the 

 more globose form of the large claws and in the o-reater relative size 

 of the left one. It occupies shells of different kinds, such as those 

 of Nerita, Turbo, &c. A still larger species, which frequents the 

 vicinity of the beach, usually selects Tttrbo shells, apparently be- 

 cause of their larger size. All the other species of Coenobita, which 

 I met with, used, when I touched them, to withdraw themselves 

 within their shells and close them up at once with their claws ; but 

 this kind, when I caught hold of the Turbo shell that it carried, left 

 the shell behind in my fingers with apparent unconcern and crawled 

 leisurely away, displaying, somewhat indecorously, the rudimentary 

 plates on the back of its abdomen. These are the plates that attain 

 their greatest development in the Cocoa-nut Crab (Birgus latro), 

 which is thus able to dispense with a shell altogether, The greatest 

 heio-hts at which I found hermit-crabs were in the island of Faro on 

 the two highest peaks, which are elevated respectively 1600 and 

 1900 feet above the sea. In both these localities, the crab had 

 reached the very summit and could not have climbed higher. The 



1 " Journal of the Beagle," p. 457. 



