ARTICULATED ANIMALS. 
480 
destitute of them. The other feet, as well as the segments to which they are attached, , 
are developed as the insect increases in age. 
There are but few vegetable substances which do not fall under the attacks of insects; 
and as those which are useful or necessary to man are not less liable to them than the | 
others, they often cause great damage, especially in seasons favourable for their multi ! 
plication. Their destruction depends greatly on our knowledge of their habits, and on 
our own vigilance. Some are omnivorous, such as the White Ants, Ants, &c., of which 
the ravages are too well known. Many among these are carnivorous ; and the species 
which feed upon carcases or excrement are a benefit conferred on us by the Author of 
Nature, and compensate, in some respect, for the losses and inconveniences which the 
others cause to us. Some species are employed in medicine and in the arts, as well as 
our domestic economy. They have also many enemies; fishes destroy a great quantity 
of aquatic species ; many birds, bats, lizards, &c., rid us of many of those which live 
upon the ground or in the air. The majority strive to avoid the dangers which menace 
their existence, by flying or running away ; but there are some which employ for this 
purpose particular stratagems or natural arms. 
Arrived at their last transformation, and enjoying all their faculties, they hasten to ; 
propagate their race; and when this is performed, their existence soon terminates. 
Thus, in our climate, each season of the year (winter excepted) presents to us many 
species which is peculiar to it. It nevertheless appears that the females, and neuters 
of those which live in society, have a longer existence. Many individuals bred in the 
autumn, conceal themselves during the rigours of winter, and reappear in the following 
spring. 
Like vegetables, the species of insects are subject to geographical limits. Those, 
for example, of the New World (with the exception of a small number of the northern 
species), are essentially peculiar to it : it also possesses many genera equally peculiar. 
The Old World, on the other hand, possesses others unknown in America. The insects 
of the south of Europe, North Africa, and the west and south of Asia, have great 
general resemblance. It is the same with those of the Moluccas, and the more eastern 
islands, including those of the South Sea. Many species of the north are found in the 
mountainous regions of more southern climates. Those of Africa differ greatly from 
those of the opposite countries of America. The insects of Southern Asia, commencing 
from the Indus or Sind, and going to the east as far as the confines of China, have 
features greatly resembling each other. The intertropical regions covered with immense 
damp forests, are the richest in insects ; and, in this respect, Brazil and Guiana are the 
most highly favoured. 
All the general systematic arrangements, relative to insects, may be essentially re- 
duced to three. Swammerdam took the metamorphosis as the base of his system ; that 
of Linnaeus is founded upon the presence or absence of wings, their number, con- 
sistence, superposition, nature of their surfaces, and upon the presence or absence of a 
sting ; whilst Fabricius only employed the parts of the mouth. The Crustacea and 
Arachnida, in all these distributions, are considered as insects ; and they are the ter- i 
minal ones in that of Linnaeus, w'hich has been generally adopted. Brisson, however, 
had separated the Crustacea as a distinct class, which he had placed before that of the | 
Insects, and which comprehended all those species which have more than six feet, — 
-namely, the Crustacea and Arachnida of Lamarck, or the Insecta Apiropoda of Savigny. | 
