GUIDE TO THE STUDY OE INSECTS. 



THE CLASS OF INSECTS. 



That branch of the Animal Kingdom known as the Artic- 

 ULATA, is so called from having the body composed of rings 

 or segments, like short cylinders, which are placed successively 

 one behind the other. Cuvier selected this term because he 

 saw that the plan of their entire organization, the essential 

 features which separate them from all other animals, lay in the 

 idea of articulation, the apparent joining together of distinct 

 segments along the line of the body. If we observe carefully 

 the body of a Worm, we shall see that it consists of a long 

 cylindrical sac, which at regular intervals is folded in upon 

 itself, thus giving a ringed (annulated, or articulated) appear- 

 ance to the body. In Crustaceans (crabs, lobsters, etc.) 

 and in Insects, from the deposition of a peculiar chemical 

 substance called cliitine, the walls of the body become so 

 hardened, that when the animal is dead and dry, it 

 readily breaks into numerous very perfect rings. 



Though this branch contains a far greater number of 

 species than any other of the animal kingdom, its myr- 

 iad forais can all be reduced to a simple, ideal, typical 

 figure ; that of a long slender cylinder divided into 

 numerous segments, as in Fig. 1, representing the larva 

 of a Fly. It is by the unequal development and the 

 various modes of grouping them, as well as the differ- 

 ences in the number of the rings themselves, and also in ^^o- 1- 

 the changes of form of their appendages, i.e. the feet, jaws, 

 antennae, and wings, that the various forms of Articulates are 

 produced. 



Fig. 1. Worm-like larva of a Fly, Scenopinus. — Original. 

 1 



