134 The Naturalist in La Plata. 



occurring in 1816, and extending over a large por- 

 tion of Europe. But in these cases the movement 

 took place at the end of May, and the insects 

 travelled due south ; their migrations were there- 

 fore similar to those of birds and butterflies, and 

 were probably due to the same cause. I have 

 been unable to find any mention of a phenomenon 

 resembling the one with which we are so familiar 

 on the pampas, and which, strangely enough, 

 has not been recorded by any European naturalists 

 who have travelled there. 



