INSECTA. 809 
the hody, and running along its whole length, named trachee. From these 
tracheal vessels are derived a great many ramifications or bronchi, the num- 
ber of which is more or less considerable, as they belong to parts enjoyimg 
more or less vital energy. The tracheee communicate with the external air by 
means of openings called sézgmata, of which the number varies, placed on 
each side of the body. In caterpillars, the number of stigmata is generally 
eighteen. These stigmata are marked in the skin of the insect by a small 
scaly plate, open in the centre, and furnished with membranes or filaments 
to protect the entrance. The larve of many species which live in water, 
have on the sides of their body, filaments or appendages in the form of 
lamin, upon which are spread vessels communicating with the bronchi and 
tracher. . 
Though insects have no lungs, and are destitute of voice properly so 
called, yet they possess the means of producing sounds. ‘Thus the male 
grasshopper makes a noise to attract the female. The males of the cicade 
and the crickets possess the same faculty. In all these insects, however, 
the means by which the sound is. produced, is similar to that by which a 
stringed instrument or drum is sounded. The males of the locust and 
grasshoppers havea portion of the internal margin of their elytra formed of an 
elastic, transparent membrane, like tale, provided with strong projecting 
ribs, separated by large hollow spaces. It is a kind of violin, of which the 
ribs represent the strings ; and the sharp, disagreeable sound by which these 
insects are distinguished ata distance, is produced by rubbing the elytra 
over one another. In the cricket, the thigh, furnished with projecting lines, 
serves as the bow, and the longitudinal ribs of the elytra the strings. In 
the cicade, the organ which produces the sound is more complicated. It is 
a species of drum, and is peculiar to themale. The abdomen, which is coni- 
cal, is provided below and near the base, with two large semicircular scales, 
which cover an empty space, in which is a delicate, tense membrane, equiva- 
lent to the skin of the drum, and below this membrane, at the bottom of the 
cavity, are other parts, which, striking against it, produce the sound. The 
stridulous noise which is heard when the Sphinx atropos is touched, is occas 
sioned by the air escaping rapidly by the trachee at the sides of the base of 
the abdomen, and which is closed in the state of repose by a bundle of stellat- 
ed hairs. Many coleoptera produce a plaintive and interrupted sound by 
_rubbing the peduncle of the base of the abdomen against the interior walls 
of the thorax; and the extremity of the head in others produces a similar 
sound. The rapid vibration of the wings is the chief cause of the humming 
noise which most insects produce when flying. 
Insects feed on all kinds of matters, vegetable and animal; and there is 
scarcely any production in these two divisions of nature, which does not serve 
as the food of some insect. Each insect, besides, has a particular food upon 
which it lives in preference, and which it is endowed with the power of dis- 
covering and procuring. Many in their perfect state live on food quite difs 
102 68* 
