480 ARTICULATED ANIMALS. 



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 (vdnter 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 rigovirs of winter, and reappear in the following 

 spring. 



Like vegetables, the species of insects are subject to geographical Hmits. 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- 

 minal ones in that of Linnaeus, which 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. 



