5690 



Crustacea. 



These observations upon the instinct that Crustacea exhibit in 

 procuring their food are exhibited from species that belong to the 

 shores of Great Britain. But the power has been as strongly exem- 

 plified in exotic tribes, as may be seen by the habits of a species of 

 Grapsus upon the small islet of St. Paul's. The noddy, a species of 

 tern, builds a simple nest with sea-weed. " By the side of many 

 of these nests, 1 ' says Mr. Darwin, in his pleasant { Naturalist's 

 Voyage,' " a small flying fish was placed, which, I suppose, had been 

 brought by the male bird for its partner. It was amusing to watch 

 how quickly a large and active crab, which inhabits the crevices of 

 the rock, stole the fish from the side of the nest as soon as we had 

 disturbed the parent birds. Sir W. Symonds, one of the few persons 

 who have landed here, informs me that he saw the crabs dragging 

 even the young birds out of their nests, and devouring them." 



T have before alluded to the Crustacea as being fond of vegetable 

 food as well as animal. A striking example we have, upon the same 

 authority as the preceding. A crab, closely allied to, if not identical 

 with, the Birgus latro (a genus near to our soldier-crab), is found on 

 all parts of the dry land, and grows to a monstrous size, on the islets 

 around Keeling Island : they live upon the cocoa-nuts that fall from 

 the trees which flourish there. " The first pair of legs terminate in 

 very strong and heavy pincers, and the last pair are fitted with others 

 weaker and much narrower. It would at first be thought quite im- 

 possible for a crab to open a strong cocoa-nut covered with husk ; 

 but Mr. Liesk assures me that he has repeatedly seen this effected. 

 The crab begins by tearing off the husk, fibre by fibre, and always 

 from that end under which the three eye-holes are situated ; when 

 this is completed, the crab commences hammering with its heavy 

 claws on one of the eye-holes till an opening is made ; then, turning 

 round its body, by the aid of its posterior and narrow pair of pincers, 

 it extracts the white albuminous substance. I think," continues Mr. 

 Darwin, u this is as curious a case of instinct as ever I heard of, and 

 likewise of adaptation in structure between two objects apparently so 

 remote from each other in the scheme of nature as a crab and a 

 cocoa-nut tree." "It has been stated by some authors that the 

 Birgos crawls up the cocoa-nut trees for the purpose of stealing the 

 nuts : I very much doubt the possibility of this ; but with the Bada- 

 nus the task would be much easier. 1 was told by Mr. Liesk that on 

 these islands the Birgos lives only on the nuts which have fallen to 

 the ground." " To show the wonderful strength of the front pair of 

 pincers, 1 may mention that Admiral Morseby confined one in a 



