1 86 The Naturalist in La Plata. 



far out at sea, it is difficult to believe that such 

 migrations take place. But where they inhabit a 

 vast area of land, as in South America, extending 

 without interruption from the equator to the cold 

 Magellanic regions, and where there is a long 

 autumn of dry, hot weather, then such an instinct 

 as migration might have been developed. For this 

 is not a faculty merely of a few birds : the impulse 

 to migrate at certain seasons affects birds, insects, 

 and even mammals. In a few birds only is it 

 highly developed, but the elementary feeling, out of 

 which the wonderful habit of the swallow has 

 grown, exists widely throughout animated nature. 

 On the continent of Europe it also seems probable 

 that a great autumnal movement of these spiders 

 takes place ; although, I must confess, I have no 

 grounds for this statement, except that the floating 

 gossamer is called in Germany " Der fliegender 

 Summer" the flying or departing summer. 



I have stated that all migrations of gossamers I 

 have witnessed have been in the autumn ; except- 

 ing in one instance, these flights occurred when the 

 weather was still hot and dry. The exceptionally 

 late migration was on March 22 a full month after 

 the departure of martins, humming-birds, fly- 

 catchers, and most other true bird-migrants. It 

 struck me as being so remarkable, and seems to 

 lend so much force to the idea I have suggested, 

 that I wish to give here an exact copy of the entries 

 made at the time and on the spot in my notebook. 



" March 22. This afternoon, while I was out 

 shooting, the gossamer-spiders presented an ap- 

 pearance quite new to me. Walking along a stream 



