126 NORTH AMERICAN INSECTS. 
as caterpillars, or in the state of chrysalis, or in their per- 
fect condition, they are always more beautiful and more in- 
teresting than all other insects, and attract more of our at- 
tention; when in the state of caterpillar, on account of the 
injury they do to vegetation, and when in their perfect form, 
on account of their splendor and variety. 
Moths and Butterflies are distinguished from other in- 
sects by having four expanded wings, with a few exceptions, 
covered with colored scales, and hairy bodies. ‘They are 
oviparous animals, and, under the guidance of their instinct, 
lay their eggs upon those plants which are best adapted for 
sustaining their future progeny. Irom these eggs proceed 
the caterpillars (larve), many of which are so voracious 
that they consume more than twice their own weight in 
twenty-four hours. We may congratulate ourselves that 
they are so small, and that we and our domestic animals 
are more moderate in our appetites; for if a man weighing 
one hundred and fifty pounds consumed every day three hun- 
dred pounds of food, or an ox weighing four hundred pounds 
devoured daily eight hundred pounds of grass, our terres- 
trial globe could not, in its present condition and extent at 
least, produce sufficient nourishment to sustain us or them. 
After it has attained its full growth the caterpillar stops 
eating 
g, casts its skin, and becomes a chrysalis or cocoon 
(pupa). Some suspend their cocoons from the branch of a 
tree, as, for instance, the Asterias; others bury themselves 
in the ground, as do all the Hawk-moths, and in this con- 
dition remain throughout the cold winter season. Thus 
the chrysalis passes its life in a state of torpor, without eat- 
ing or moving, until, after a shorter or longer period, it 
bursts its skin, and the perfect butterfly or moth issues, no 
more to injure vegetation, because it has exchanged its 
mouth for a spirally rolled tongue, with which it can only 
suck the juices of plants and flowers. 
In this metamorphosis some very great changes occur in 
