38 NORTH AMERICAN INSECTS. 



name Insect. Each of these has, at least, six legs, when 

 in a perfect condition. 



Although Insects differ from the vertebrate animals, 

 viz., from Beasts, Birds, Reptiles, and Fishes, which are 

 provided with a bony frame and red blood, still they 

 are entirely analogous to them in regard to many of 

 their physical functions, in nervous Sensation and 

 Perception, in regard to Respiration, which is effected 

 by respiratory organs, or air-holes placed on the hind 

 body, and in regard to Nutrition, which is effected 

 through a stomach and intestines. 



Insects are found in the air, as, for instance, Butter- 

 flies ; or in the water, as the whirling Water-beetle ; or 

 in the ground, as the Centipede ; or on plants, as the 

 Caterpillars ; or upon the body of animals, as Ticks and 

 other Spongers. 



There is scarcely a plant or an animal which is not 

 the dwelling of some Insect. Hence the number of 

 Insects must be immense, and without exaggeration, it 

 may be said, that there are in existence more than a 

 hundred thousand different species. If we adopt the 

 general rule, that on an average, three species of Insects 

 dwell on each species of plants, (Ynd on some plants we 

 find three or four times as many,) we can easily see 

 that such an enormous number cannot prove too small an 

 estimate, when Ave consider that there are now known 

 between forty and fifty thousand species of plants. 



