INSECTS. PAA S| 
CHAPTER XXII. 
INSECTS. 
379. THE sub-kingdom which we have already consid- 
ered is the Vertebrate. The other three sub-kingdoms 
are said to be Invertebrate, the prefix 77 being here used 
as meaning the same as the very common negative prefix 
un. Of these sub-kingdoms I will notice the Articulata 
first. The two chief characteristics of it were stated in 
Chapter I. These, however, and other characteristics, 
require a more particular notice here, before I enter on 
the consideration of Insects, the special subject of this 
chapter. 
380. The kingdom of the Articulates includes a wide 
range of animals of great variety — Insects, Worms, the 
Spider and Scorpion tribe, and the Crab tribe. But they 
all agree in one thing—in having a covering which an- 
swers the purpose of the internal skeleton of the Verte- 
brates. This covering, or jointed armor, gives firmness 
to the body, and furnishes points of attachment to the 
muscles. 
381. This skeleton coat of mail is very commonly ar- 
ranged on the bodies of these animals in segments in the . 
form of rings. This arrangement is seen most perfectly 
carried out in the Centipede, Fig. 178 (p. 226). You can 
also see it plainly in the bodies of most insects, as, for ex- 
ample, in the common Fly. This arrangement mostly 
disappears in the Crab tribe, where, for the sake of firm- 
ness, the skeleton covering the body of the animal is in 
one piece. So, also, on the other hand, it nearly disap- 
pears in such soft Articulates as the Leech and Earth- 
worm, because there the rings would not allow the requi- 
site limberness. 
Ke 
