i64 INSECTS AT. SEA. [chap. viii. 



(two species), Notaphusy Cynucus, Adimonia, and Scara- 

 bcBus. 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 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 grass- 

 hopper (Acrydium), which flew on board when the Beagle 

 was to windward of the Cape de Verd Islands, and when 

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

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

 hundred and seventy 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 

 ist, 1832) I paid particular attention 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 colour, 

 were attached to the webs. There must have been, T 

 should suppose, some thousands on the ship. The little 

 spider, when first coming in contact with the rigging, 

 was always seated on a single thread, and not on the 

 flocculent mass. This latter seems merely to be pro- 

 duced by the entanglement of the single threads. The 

 spiders were all of one species, but of both sexes, together 

 with young ones. These latter were distinguished by 

 their smaller size and more dusky colour. I will not 



* The flies which frequently accompany a ship for some days on its 

 passagfe from harbour to harbour, wandering from the vessel, are soon lost, 

 anH all disappear. 



