1838. HOUSE—No. 72. 59 
skin of the back, represents the heart, and contains a pale-colored 
blood, which flows, with a wavy motion, from the tail to the head, 
and thence penetrates into the various crevices within the body. 
Insects do not breathe through their mouths, and have no lungs ; 
they imbibe the air by means of several lateral pores called spiracles, 
from which it is distributed to every part of the body through certain 
tubes called tracheez and bronchie, which thus perform the office of 
lungs. 
These constitute the principal peculiarities of their internal struc- 
ture. But the most wonderful characteristic of insects is this. In 
order to arrive at the full and complete possession of their powers, 
they must pass through three successive stages, in which they exhibit 
a greater orless change of forms. This change of form is called met- 
amorphosis, which signifies transformation. The caterpillar, or grub, 
after feeding a certain time, casts off its skin and assumes a different 
shape, in which it remains at rest and takes no food ; sooner or later 
this second state is succeeded by another: the insect throws off its 
sluggish habit, emerges from the case or bandages in which, like a 
mummy, it was enveloped, and appears a renovated or resuscitated, 
volatile being, endued with new organs, and feeling the impulses of 
unknown passions. ‘This is the perfect state, in which only it is ca- 
pable of providing for a continuation of the species. 
All insects, however, do not exhibit so great a dissimilarity in their 
three stages, and some, in the second, are capable of moving about, 
and even take food. ‘The first state, in which an insect appears at 
its birth, is called the larva ; when it changes from this, it becomes a 
chrysalis or pupa ; the last metamorphosis produces the insect in its 
perfect state, the tmago, image, or correct representation of the 
species. 
The perfect insect has only six legs ; its head is distinct ; its 
eyes are compound, or composed of a great number of single eyes 
closely united together, and incapable of being rolled in their sockets. 
It has a pair of organs, situated near the eyes, called antenne, 
which are the external recipients of some of their senses. The 
body is divided into three principal parts called, head, thorax, and 
abdomen. ‘The situation of the head is obvious ; the thorax is placed 
immediately behind it; the abdomen constitutes the posterior and 
