DRAGONFLIES. 181 



nor "historical memory" — as the present phase of Dr. Erasmus 

 Darwin's old tradition theory is called — will account for the 

 Dragonfly storms, as the phenomena of the Pampas might be 

 called, since the insects do not pass and repass between " breeding 

 and subsistence areas," but all journey in a north-easterly direc- 

 tion; and of the countless millions flying like thistle-down before 

 the great pampero wind, perhaps, not one solitary traveller ever 

 returns. 



The cause of the flight is probably dynamical, affecting the 

 insects with a sudden panic, and compelling them to rush away 

 before the approaching tempest. The mystery is that they should 

 fly from the wind before it reaches them, and yet travel in the 

 same direction with it. When they pass over the level treeless 

 country, not one insect lags behind, or permits the wind to over- 

 take it ; but on arriving at a wood or large plantation, they swarm 

 into it, as if seeking shelter from some swift-pursuing enemy, and 

 on such occasions they sometimes remain clinging to the trees 

 while the wind spends itself. This is particularly the case when 

 the wind blows up at a late hour of the day ; then, on the following 

 morning, the Dragonflies are seen clustering to the foliage in such 

 numbers that many trees are covered with them, a large tree often 

 appearing as if hung with curtains of some brown glistening 

 material, too thick to show the green leaves beneath. 



In Patagonia, where the phenomenon of Dragonfly storm is 

 also known, an Englishman residing at the Rio Negro related to 

 me the following occurrence, which he witnessed there : — A race 

 meeting was being held near the town of El Carmen, on a high 

 exposed piece of ground, when, shortly before sunset, a violent 

 pampero wind came up, laden with dense dust-clouds. A few 

 moments before the storm broke, the air all at once became 

 obscured with a prodigious cloud of Dragonflies. About a hundred 

 men, most of them on horseback, were congregated on the course 

 at the time, and the insects, instead of rushing by in their usual 

 way, settled on the people in such quantities that men and horses 

 were quickly covered with clinging masses of them. My informant 

 said, and this agrees with my own observation, that he was greatly 

 impressed by the appearance of terror shown by the insects ; 

 they clung to him as if for dear life, so that he had the greatest 

 difficulty in ridding himself of them. 



Weissenborn, in Loudon's ' Magazine of Natural History ' 



