INSECTS AND THEIR ALLIES. 
BY A. 8. PACKARD, JR., M: D. 
That branch of the Animal Kingdom known as the., 
ARTICULATA, 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 or- 
ganization, the essential features which separate them 7} 
from all other animals, lay in the idea of articula- 
tion, the apparent joining together of distinct seg- 
ments along the line of the body. If we observe 
carefully the body of the Worm, we shall see that it 
consists of a long cylindrical sac, which at regular 
intervals is folded in upon itself, thus giving a ring- 
ed,annulated or articulated appearance to the body. 
In the Crustacea (Crabs, Lobsters, ete.) and in the 
Insects, from the deposition of an earthy salt, called . 
chitine, the walls of the body become so hardened, jarva of 
that when the animal is dead and dry, it readily mereva? nano 
breaks into numerous very perfect ri 
Though this branch contains a far picsa number of 
` species than any other of the animal lecnigeloens: their myriad 
forms 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 differences in the number 
of the rings themselves, and also in the changes of form 
of their appendages, i. e., the feet, jaws, antennæ and 
wings, that the various forms of Articulates are produced. 
In all Articulates the long, tubular, alimentary canal 
occupies the centre of the body ; above it lies the “heart,” 
AMERICAN NAT. VOL. I. 10 
