185 



CHAPTER IX. 



Rio Plata — Flocks of butterflies — Beetles alive in the sea — Aeronaut 

 spiders — Pelagic animals — Phosphorescence of sea — Port Desire — 

 Spanish settlements — Zoology — Guanaco — Excursion to head of har- 

 bour — Indian grave — Port St. Julian — Geology of Patagonia, succes- 

 sive terraces, transport of pebbles— Fossil gigantic llama — Types of 

 organization constant — Change in zoology of America — Causes of 

 extinction. 



PATAGONIA. 



December 6th^ 1833. — The Beagle sailed from the Rio 

 ?lata, never again to enter its muddy stream. Our course 

 \^as directed to Port Desire, on the coast of Patagonia. 

 Btfore proceeding any further, I will here put together a 

 fe^ observations made at sea. 



kfeveral times when the ship has been some miles off the 

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

 of ISirthern Patagonia, we have been surrounded by in- 

 sects. One evening, when we were about ten miles 

 from tie Bay of San Bias, vast numbers of butterflies, 

 in banis or flocks of countless myriads, extended as far 

 as the tye could range. Even by the aid of a glass it 

 was not 7ossible to see a space free from butterflies. The 

 seamen cied out "it was snowing butterflies,^^ and such in 

 fact was til? appearance. More species than one were pre- 

 sent, but tie main part belonged to a kind very similar to, 

 but not ideitical with, the common English Colias edusa.^ 

 Some moths and hymenoptera accompanied the butterflies; 

 and a fine Calosoma flew on board. Other instances are 

 known of thisbeetle having been caught far out at sea ; and 

 this is the moe remarkable, as the greater number of the 

 Carabidee seldoii or never take wing. The day had been 



* I am indebtedto Mr. Waterhouse for naming these and otlier 

 insects. \ 



