158 RIO PLATA. [chap. viii. 



have been brought up by their unnatural parent, Spain, should 

 always be borne in mind. On the whole, perhaps, more credit 

 is due for what has been done, than blame for that which may be 

 deficient. It is impossible to doubt but that the extreme liberalism 

 of these countries must ultimately lead to good results. The very 

 general toleration of foreign religions, the regard paid to the 

 means of education, the freedom of the press, the facilities 

 offered to all foreigners, and especially, as I am bound to add, to 

 every one professing the humblest pretensions to science, should 

 be recollected with gratitude by those who have visited Spanish 

 South America. 



December 6th. The Beagle sailed from the Rio Plata, 

 never again to enter its muddy stream. Our course was directed 

 to Port Desire, on the coast of Patagonia. Before proceeding 

 any further, I will here put together a few observations made at 

 sea. 



Several times when the ship has been some miles off the mouth 

 of the Plata, and at other times when off the shores of Northern 

 Patagonia, we have been surrounded by insects. One evening, 

 when we were about ten miles from the Bay of San Bias, vast 

 numbers of butterflies, in bands or flocks of countless myriads, 

 extended as far as the eye could range. Even by the aid of a 

 telescope it was not possible to see a space free from butterflies. 

 The seamen cried out " it was snowing butterflies," and such in 

 fact was the appearance. More species than one were present, 

 but the main part belonged to a kind very similar to, but not 

 identical with, the common English Colias edusa. Some moths 

 and hymenoptera accompanied the butterflies ; and a fine beetle 

 (Calosoma) flew on board. Other instances are known of this 

 beetle having been caught far out at sea ; and this is the more 

 remarkable, as the greater number of the Carabidss seldom or 

 never take wing. The day had been fine and calm, and the one 

 previous to it equally so, with light and variable airs. Hence 

 we cannot suppose that the insects were blown off the land, but 

 we must conclude that they voluntarily took flight. The great 

 bands of the Colias seem at first to afford an instance like those 

 on record of the migrations of another butterfly, Vanessa cardui ;* 



* Lyell's Principles of Geology, vol. iii. p. 63. 



