2IO INSECT MIGRATION 



birds, and all fail when other facts, or when all the 

 facts, are considered — that is to say, the facts con- 

 cerning bird migration. What shall we then say of 

 them when we look from birds to other beings — 

 fishes, mammals, insects, and even spiders ? For in 

 all these classes we find migration, and it is quite 

 probable that the inhabitants of the sea are as 

 regularly and as powerfully moved by the impulse 

 as the fowls of the air. 



The subject of fish migration is now being investi- 

 gated; from personal observations I know nothing 

 about it, and as to insect migration I know very 

 little. The little I have seen, however, has served 

 to convince me that there are great occasional 

 migratory movements corresponding in time and 

 direction to the seasonal migration of birds, and I 

 conclude that they are due to the same compelling 

 force. From what one has read, one thinks chiefly of 

 locusts, dragon-flies and butterflies in this connection. 



The grasshopper plague was of frequent occurrence 

 on the pampas in my time; but this insect was in- 

 capable of sustained flight, and the movement was a 

 sort of drifting, flying and settling and feeding as 

 they went, as a rule in a southerly direction. The 

 migratory locust was unknown in southern Argentina. 

 Only once, about midsummer, we saw a cloud coming 

 from the north, which turned out to be a flight of 

 locusts that must have travelled several hundreds of 

 miles from the sub-tropical northern provinces of the 

 country. The cloud settled in my district, and there 

 remained and laid its eggs. People looked appre- 



