204 RIO PLATA. 



had been blown from the shore ; but upon reflect- 

 ing that out of the eight species four were aquatic, 

 and two others partly so in their habits, it appeai'- 

 ed to me most probable that they were floated into 

 the sea by a small stream which drains a lake near 

 Cape Con-ientes. On any supposition, it is an in- 

 teresting circumstance to find live insects swim- 

 ming 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 obsei-ved 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 insect on the wing, with an off"- 

 shore breeze, would be very apt to be blown out to 

 sea. The most remarkable instance I have known 

 of an insect being caught far from the land, was 

 that of a large grasshopper (Acrydium), which 

 flew on board when the Beagle was to windward 

 of the Cape de Verd Islands, and when the near- 

 est point of land, not directly opposed to the trade- 

 wind, was Cape Blanco on the coast of Africa, 370 

 miles distant.* 



On several occasions, when the Beagle has been 

 within the mouth of the Plata, the rigging has been 

 coated with the web of the Gossamer Spider. One 

 day (November 1st, 1832) I paid particular atten- 

 tion to this subject. The weather had been fine 

 and clear, and in the morning the air was full of 

 patches of the flocculent web, as on an autumnal 

 day in England. The ship was sixty miles distant 

 from the land, in the direction of a steady though 

 light breeze. Vast numbers of a small spider, about 

 one tenth of an inch in length, and of a dusky red 



* The flies which frequently accompany a ship for some days 

 on its passage from harbour to harbour, wandering from the ves- 

 sel, are soon lost, and all disappear. 



