xii GEOGRAPHICAL DISTRIBUTION OF ORGANISMS 359 



supplies the innumerable stragglers which every year reach 

 Bermuda and the Azores. 



Insects. 



Winged insects have been mainly dispersed in the same 

 way as birds, by their power of flight, aided by violent or long- 

 continued winds. Being so small, and of such low specific 

 gravity, they are occasionally carried to still greater distances ; 

 and thus no islands, however remote, are altogether without 

 them. The eggs of insects, being often deposited in borings 

 or in crevices of timber, may have been conveyed long 

 distances by floating trees, as may the larvae of those species 

 which feed on wood. Several cases have been published of 

 insects coming on board ships at great distances from land ; 

 and Darwin records having caught a large grasshopper when 

 the ship was 370 miles from the coast of Africa, whence the 

 insect had probably come. 



In the Entomologists Monthly Magazine for June 1885, Mr. 

 MacLachlan has recorded the occurrence of a swarm of moths 

 in the Atlantic ocean, from the log of the ship Pleione. 

 The vessel was homeward bound from New Zealand, and in 

 Lat. 6° 47' K, Long. 32° 50' W., hundreds of moths appeared 

 about the ship, settling in numbers on the spars and rigging. 

 The wind for four days previously had been very light from 

 north, north-west, or north-east, and sometimes calm. The north- 

 east trade wind occasionally extends to the ship's position at 

 that time of year. The captain adds that "frequently, in 

 that part of the ocean, he has had moths and butterflies 

 come on board." The position is 960 miles south-west of 

 the Cape Verde Islands, and about 440 north-east of the 

 South American coast. The specimen preserved is Deiopeia 

 pulchella, a very common species in dry localities in the 

 Eastern tropics, and rarely found in Britain, but, Mr. Mac- 

 Lachlan thinks, not found in South America. They must 

 have come, therefore, from the Cape Yerde Islands, or from 

 some parts of the African coast, and must have traversed 

 about a thousand miles of ocean with the assistance, no doubt, 

 of a strong north-east trade wind for a great part of the distance. 

 In the British Museum collection there is a specimen of the 

 same moth caught at sea during the voyage of the Rattlesnake, 



