RIO PLATA 
CHAP. 
168 
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 
Carabidae 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 ; 1 but the presence of other 
insects makes the case distinct, and even less intelligible. 
Before sunset a strong breeze sprung up from the north, and 
this must have caused tens of thousands of the butterflies and 
other insects to have perished. 
On another occasion, when seventeen miles off Cape 
Corrientes, I had a net overboard to catch pelagic animals. 
Upon drawing it up, to my surprise I found a considerable 
number of beetles in it, and although in the open sea, they did 
not appear much injured by the salt water. I lost some of the 
specimens, but those which I preserved belonged to the genera 
Colymbetes, Hydroporus, Hydrobius (two species), Notaphus, 
Cynucus, Adimonia, and Scarabseus. At first I thought that 
these insects had been blown from the shore ; but upon reflecting 
that out of the eight species four were aquatic, and two others 
partly so in their habits, it appeared to me most probable that 
they were floated into the sea by a small stream which drains a 
lake near Cape Corrientes. On any supposition it is an 
interesting circumstance to find live insects swimming in the 
open ocean seventeen miles from the nearest point of land. 
There are several accounts of insects having been blown off 
the Patagonian shore. Captain Cook observed it, as did more 
lately Captain King in the Adventure. The cause probably is 
due to the want of shelter, both of trees and hills, so that an 
1 LyeJl’s Principles of Geology, vol. iii. p. 63. 
