MIGRATION. 177 



As we have been reviewing, in a cursory 

 manner, the laws of migration, selecting byway 

 of illustration the habits of various animals, 

 with which we are more or less familiar, we 

 would here add an observation relative to the 

 periodical, but limited migrations of certain 

 species of crabs, (or Crustacea,) which are not 

 destitute of considerable interest. Many crabs 

 (as those of the genera Ocypoda, Gelasimus, 

 etc.,) are semi-aquatic ; but some are much less 

 aquatic than others, and some not only migrate, 

 but also hybernate. As an example in point, 

 we may first notice the sand-crab of Catesby, 

 (Ocyoda armaria,) a native of the coasts of 

 America and the Antilles. The habits of this 

 species are very singular. During the whole of 

 the summer the animal lives on the sea-shore, 

 where it excavates for itself a burrow three or 

 four feet in depth, above the highest line of the 

 tides, or even the dash of the waves. In this 

 burrow it secludes itself during the day, but 

 comes abroad on the approach of dusk, to roam 

 in quest of food. It now visits the shore, 

 traverses the wet sands, and dabbles in the 

 pools. Upon any alarm, it scuds away with 

 great rapidity, at the same time elevating its 

 claws, as if to warn the pursuer of its resolution 

 to defend itself. Towards the end of October, 

 troops of these crabs leave the sea-side and 

 journey inland, in search of some suitable spot 

 where, like marmots, they may excavate deep 

 burrows in which to hybernate. Into these 

 burrows they retire, and stop up the entrance 



