380 



GEOGRAPHICAL DISTEIBUTION AND 



[Ch. XL. 



the LibelMse, Coccinellse^ Carabi^ Cicadse, &c.^ are not 

 usually social insects ; but seem to congregate^ like swallows, 

 merely for the purpose of emigration."^" Here, therefore, we 

 have an example of an instinct developing itself on certain 

 rare em-crgencies, causing unsocial species to become gre- 

 garious and to venture sometimes even to cross the ocean. 



The armies of locusts {Gryllus migratorius)^ which darken 

 the air in Africa and traverse the globe from Turkey to our 

 southern counties in England, are well known to all, and their 

 vast geographical range will again be alluded to (Chap.XLII.). 

 When the western gales sweep over the Pampas they bear 

 along with them myriads of insects of various kinds. As a 

 proof of the manner in which species may be thus diffused, I 

 may mention that when the Creole frigate was lying in the 

 outer roads off Buenos Ayres, in 1819, at the distance of 

 six miles from the land, her decks and rigging were suddenly 



The 

 sides of the vessel had just received a fresh coat of paint, 



to which the insects adhered in such numbers as to spot 

 and disfigure the vessel, and to render it necessary partially 

 to renew the paint.f The late Admiral W. H. Smyth was 

 obliged to repaint his vessel, the Adventure, in the Mediterra- 

 nean, from the same cause. He was on his way from Malta 

 to Tripoli, when a southern wind blowing from the coast of 

 Africa, then one hundred miles distant, drove such myriads 

 of flies upon the fresh paint, that not the smallest point was 

 left unoccupied by insects. 



Moths seen flying 300 miles from land. — Captain Henry 

 Toynbee has put on record some striking examples of the 

 great distance from land at which the larger Lepidoptera are 



covered with thousands of flies and grains of sand. 



occasionally seen on the 



wmg. 



A female of the large 



Sphynx ConvolvitU flew on board his ship, the Hotspur, East 

 Indiaman, in lat. 1 2° 09' K and long. 21^ 1 7' W., a point 300 

 miles from the nearest coast of Africa, and about 210 miles 

 from the Cape de Yerde Islands, from which last it is 

 supposed to have come, as the prevailing winds at the time 

 were north-westerly. Two individuals of the common Death's 



I 



* Kirby and Spence, vol. ii. p. 9. 



1817. 



t lam indebted to Lieutenant Graves 

 K.N. for this information. 



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