NATURAL HISTORY OF AFRICA. 465 
situations ; others are much more limited, both in 
their geographical and physical distribution. In the 
vegetable kingdom, we observe the same species un- 
der different latitudes, exhibiting different intensi- 
ties, and even tints of colour. ^The same is the case 
with insects. Even the same kind of colour changes 
according to the situation, becoming deeper and 
paler, and more or less metallic or silky. But the 
habits, manners, and uses of this wonderful class of 
animals are those that most powerfully arrest the 
attention of the general observer. We shall now 
therefore notice a few species in these respects, it 
not being our intention to enter particularly into 
the history of African insects. 
The migratory locust (gryllus migratorius, Lin.) 
is the most formidable insect met with in Africa. 
Its incalculable numbers, and extraordinary vora- 
city, have, in all ages, caused it to be considered 
as one of the most calamitous visitants of the dis- 
tricts where it appears. Whole provinces are ra- 
vaged and destroyed by them ; wherever their my- 
riads spread, the verdure of the country disappears ; 
trees and plants are stripped of their leaves, and re- 
duced to their naked boughs and stems ; and every 
thing green is as completely destroyed as if the 
country had been exposed to the ravages of fire. 
When these clouds of locusts take their flight, the 
heavens are literally darkened by them. The ce- 
lebrated traveller Barrow gives a very striking pic- 
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