286 MENTAL EVOLUTION IN ANIMALS. 



The caterpillar of this species is not gregarious. Professor 

 Bonelli also describes a migration similar in all respects, 

 including locality, except that it lasted longer — the insects 

 covering the flowers at night and proceeding on the journey 

 by day. 



Immense swarms of migratory Dragon-flies have been at 

 times observed, the most remarkable case being one that 

 occurred in May, 1839, and which seems to have extended 

 over a great part of Europe. The insects flew at a height of 

 100 to 150 feet, and seemed to follow the direction of the 

 rivers.* 



Many species of Fish are known to migrate regularly for 

 purposes of spawning, such as the herring, salmon, &c, and 

 also to find water ; f while among Eeptiles the most remark- 

 able instance seems to be that which is furnished by tire 

 Turtles which visit Ascension Island to deposit their eggs. 

 How the animals can find this comparatively small speck of 

 land in the midst of a vast ocean is very unaccountable. I 

 have recently written to Professor Moseley upon the subject, 

 and in reply he says, " No man without proper modern 

 means of finding latitude and longitude could reach either 

 Tristan or Ascension ; and it is especially difficult for 

 animals whose eyes cannot be raised above the sea-level, and 

 to whom, therefore, the islands are visible for a comparatively 

 small radius only. Merchant skippers have several times 

 been unable to find Bermuda, and on return baffled have 

 reported the island gone down." But, as Professor Moseley 

 adds, " It is just possible that the animals do not retire far 

 from the land after all, but hang about unobserved," I think 

 it is undesirable to enter into any discussion where the facts 

 are still of an uncertain character. 



Among Mammals, from whales to mice, we meet with 

 many migratory species, but it is among Birds that the 

 propensity is most prevalent. Indeed, a very competent 

 authority on all matters pertaining to ornithology has said in 

 the new " Encyclopaedia Britannica : " " Every bird of the 

 northern hemisphere is to a greater or less degree migratory 

 in some part of its range. Such a conclusion brings us to a 

 still more general inference — viz., that Migration, instead of 



* For a full account see Weissenborne, Loundouri's Meg. Nat. RUt., 

 N.S., vol. iii. 



t See Animal Intelligence, 218-50. 



