176 WONDERS OF ORGANIC LIFE. 



dried up the lichens on the barren grounds, 

 and the caribou frequents the moist pastures, 

 which cover the narrow valleys on the coasts 

 and islands of the Arctic Sea, where they graze 

 on the sprouting carices, and on the withered 

 grass or hay of the preceding year, which at 

 that period is still standing and retaining part 

 of its sap. The spring journey is performed 

 partly on the snow, and partly after the snow 

 has disappeared, on the ice covering the rivers 

 and lakes, which have in general a northernly 

 direction." 



The North American bison is also migratory 

 in its habits, but its migratory movements 

 appear to be irregular. Herds, often consisting 

 of many thousands, wander over the prairies 

 watered by the Arkansas, Plata, Missouri, and 

 the upper branches of the Saskatchewan and 

 Peace rivers, changing their pasture grounds, and 

 often visiting the salt springs or saline morasses. 



Among insects, the swarming and departure 

 of bees from the old hive in quest of a new 

 habitation may be considered as an irregular 

 migratory movement, and so may the swarming 

 and flight of clouds of ants issuing forth to 

 found a new colony. 



The locust also affords us a remarkable 

 example of irregular migration as performed by 

 insects. We might here fill some pages with 

 details, but the subject has been so fully 

 discussed, and so many popular accounts have 

 been given, that we shall not trouble our 

 readers with a narrative of them. 



