186 



RIO PLATA. 



Dec. 1833. 



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 Vanessa cardui;* but the presence of other 

 insects makes the case distinct, and not so easily intelligible. 

 Before sunset, a strong breeze sprung up from the north, 

 and this must have been the cause of tens of thousands 

 of the butterflies and other insects having 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, thef 

 did not appear much injured by the salt water. I lost sonre 

 of the specimens, but those which I preserved, belonged to 

 the genera, colymbetes, hydroporus, hydrobius (two speciis), 

 notaphus, cynucus, adimonia, and scarabseus. At firs^, I 

 thought that these insects had been blown from the slore ; 

 but upon reflecting that out of the eight species, fourwere 

 aquatic, and two others partly so in their habits, it appeared 

 to me most probable that they were floated into tie sea, 

 by a small stream which drains a lake near Cape Corientes. 

 On any supposition, it is an interesting circumstance to find 

 insects, quite alive, swimming in the open ocean, seventeen 

 miles from the nearest point of land. There ffe several 

 accounts of insects having been blown off the Patagonian 

 shore. Captain Cook observed it, as did more lafely Captain 

 King in the Adventure. The cause probably is di3 to the want 

 of shelter, both of trees and hills, so that an nsect on the 

 wing with an off-shore breeze, would be very a^t to be blown 

 out to sea. The most remarkable instance ' ever knew of 

 an insect being caught far from the land, wa that of a large 

 grasshopper [Acrydium)^ which flew on loard, when the 



* Ly ell's Geology, vol. iii., p. 6- 



