302 THE CAUSES WHICH 



could see, having the appearance of black drifting snow, if I 

 may so call it. By one o^clock the flight had completely passed; 

 the wind at the time was blowing fresh from the south-east. 

 In the afternoon, on sailing up the channel of Corfu, the traces 

 of the passage of the flight were very evident from the quan- 

 tities of dead butterflies which floated on the surface of the 

 water ; and for days afterwards they were to be seen drifting 

 into the various bays in the island of Corfu. I did not hear 

 whether this flight had been observed on the Continent, but 

 as tlieij appeared to he taking the direction of the coast of Italy 

 they would, in all probability, strike the land in the vicinity of 

 Otranto.^^ 



Onward through Italy proceed these insect-chains. Thus the 

 late Professor Bonelli, of Turin,^ one year in the beginning of 

 the present century, observed a similar flight of the same species 

 of butterfly towards the end of March. " Their flight was from 

 south to north, and their numbers were so immense that at night 

 the flowers were literally covered with them. As the spring 

 advanced their numbers diminished, though even in June a few 

 still continued. ^^ Then we come to Madame de Meuran Wolff^s 

 account. " She had gone on this or a subsequent summer to 

 Grandson, and was enjoying the prospect of the lake of Neuf- 

 chatel and charming Swiss mountains. It was the begimiing 

 of June, we believe, when this lady abserved with surprise an 

 immense flight of butterflies traversing her little garden with 

 great rapidity. They were all of the species called Belle Dame, 

 and were flying close together in the same direction from south 

 to north, and were so little afraid when any one approached 

 that they never turned to the right or to the left. The flight 

 continued for two hours without interruption, and the column 

 was about ten or fifteen feet broad. They did not stop to alight 

 on flowers, but flew onwards, low and equally.'"' Their line of 

 migration still strikes northward. On the 20th of June, 1879, 

 the following notice appeared in the Daily Telegraph : — " Still 

 bent on showing itself extraordinary, eccentric, and unparalleled, 

 this year of floods, earthquakes, eruptions, and general crises is 

 determined to be remarkable also for entomological manifesta- 



* J. Rennie, "Insect Miscel.," p. 266. 



