146 VORACITY OF INSECTS. 



Some feed only upon the outside of the leaves ; sortie upon 

 the internal tissue ; others upon the flowers or on the fruit ; 

 a few will eat nothing but the bark ; while many derive their 

 nourishment only from the woody substance of the trunk. 



146. The excessive multiplication of certain tribes of 

 Insects has sometimes had the effect of devastating an entire 

 country. Thus the " plague of locusts " is not unfrequently 

 repeated in tropical countries, and is dreaded by the inhabi- 

 tants even more than an earthquake. These insects are of 

 such extreme voracity that no green thing escapes them; 

 and when their numbers are so increased that they fly in 

 masses which look like dark clouds, and cover the ground 

 where they alight for miles together, it may be easily con- 

 ceived that the devastation they create must produce incal- 

 culable injury. The north of Africa and the west of Asia are 

 the countries most infested by these pests. It is related by 

 Augustin, that a plague, induced partly by the famine they 

 had created, and partly by the stench occasioned by their 

 dead bodies, carried off 800,000 inhabitants from the kingdom 

 of Numidia and the adjacent parts. They occasionally attack 

 the south of Europe. It is recorded that Italy was devastated 

 by them in the year 591 ; and that a prodigious number both 

 of men and beasts perished from similar causes, no less 

 than 30,000 persons in the kingdom of Venice alone. These 

 tremendous swarms usually advance towards the sea ; and 

 being there checked, and having completely exhausted the 

 country behind them, they themselves die of famine, or are 

 blown into the sea by a gale. In 1784 and 1797, they de- 

 vastated Southern Africa ; and it is stated by Mr. Barrow 

 (in his Travels in that country) that they covered a surface 

 of 2,000 square miles; that, when cast into the sea by a 

 strong wind from the north-east, and washed upon the beach, 

 they formed a line fifty miles long, and produced a barrier 

 along the coast three or four feet high ; and that, when the 

 wind again changed, the stench created by the putrefaction 

 of their bodies was perceived at a distance of 150 miles 

 inland. A similar event occurred in the Earbary States in 

 1799, and was followed, as in the other cases, by a plague. 



147. We have occasionally an example of similar devasta- 

 tion in our own country, though on a smaller scale. Thus, 

 a few years ago, the turnip-crops of some parts of England 



