538 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 49. 



Along the marsh-to-swamp-to-land route a number of crustaceans 

 have traveled. Most entomostracans in fresh water probably came 

 this way but have never attained as far as the land. Possibly some 

 shrimps (Palaemonetes) and crabs (Trichodactylus) have also taken 

 this route, the latter reaching the land. 



The seclusive habits of crustaceans have been a great help to them 

 in their landward migration. Most terrestrial species are burrowers 



\ MOUNTAINS / 



\ 





LAND 





OCEIAN 



Fig. 2.— Diageam to show the crustaceans in various habitats in Colombia and their migration 



ROUTES. 



or live under leaves or fallen logs during the day. They are thus 

 better protected from then- predaceous enemies and are less exposed 

 to dessication. Starting on the wet beaches along the shores of the. 

 ocean or of rivers, there has been a gradual migration to damp places 

 under stumps, stones, and leaves, and from such situations even to 

 arboreal habitats, under bark or among foUage. In figure 2 the 

 chief routes of travel are shown. 



