264 HABITS AND INSTINCTS OP ANIMALS. CHAP. VIII. 



perate and tropical regions ; but it te in the Old World, 

 alone, that those particular species are found, of which 

 we are now to speak. How these insects are multiplied 

 to -such an excess in some particular years, and not in 

 others, has never yet been ascertained, and, perhaps, 

 never will be. The appearance of the locusts which 

 caused such terrible devastation in Central Europe, 

 in the year 1747; is thus described : " One of these 

 columns, which entered Transylvania in August, was 

 several hundred fathoms in width, and extended to so 

 great a length as to be four hours in passing over the 

 Red Tower ; and such was its density, that it totally 

 intercepted the solar light, so that when they flew 

 low, one person could not see another at the distance of 

 twenty paces. The breadth of this column, at Vienna, 

 was calculated at three miles." This, however, was 

 but a small detachment, or a straggling party, when 

 compared to that witnessed by major Moore in India. 

 He relates that, when at Poonah, he was witness to an 

 immense army of locusts which ravaged the Mahratta 

 country. He was assured that this column extended 

 500 miles, and so compact was it when on the wing, 

 that, like an eclipse, it completely hid the sun. Dr. 

 Clarke compares a flight which he witnessed to a 

 shower of snow, when the flakes are carried obliquely 

 by the wind. Mr. Barrow speaks of another, seen 

 in the southern parts of Africa in 1 797 : an area of 

 nearly 2000 square miles might be said literally to be 

 covered by them : when driven into the sea by a north- 

 west wind, they formed upon the shore, for fifty miles, 

 a bank three or four feet high ; and when the wind was 

 south-east, the stench was so powerful as to be smelt at 

 the distance of 150 miles.* Migrations of locusts, 

 and, indeed, of nearly all other insects, never occur, like 

 those of quadrupeds and birds, at stated times and sea- 

 sons ; on the contrary, they seem to depend on various 

 concurrent causes, which are far beyond our reach of 

 knowledge. To this, however, there is one exceptipn, 



* Trav. p. 257. 



