ORDER IV.—MOTHS AND BUTTERFLIES. 135 
tend to the hind part of the body, and thence back to the 
neck, where they open at the inferior lip. ‘Those tubes con- 
tain the substance which the animal uses in spinning, which 
is a yellow or white juice, according to the food it takes, 
and upon this also probably depends the fineness of the silk 
they make, in the same manner as the quality and color of 
butter depends upon the food of the cow. 
These tubes joining together and opening at the under 
lip, constitute the spinning apparatus of caterpillars, and 
may be distinctly seen by opening with great care and cau- 
tion the back of the animal. The juice contained in the 
tubes is nothing more nor less than a kind of very fine var- 
nish, of which the people of some countries make use, but 
which no one has yet undertaken to use in this country. 
Should this varnish ever come into general use, our most 
noxious caterpillars would become beneficial to us. 
Figure 27, 

Saturnia Io.—Male. 
The single parts of Moths and Butterflies, although not 
quite as varied and complex as those of caterpillars, still 
present some points of interest and curiosity, and far excel 
them in beauty and splendor. : 
The four wings of Moths and Butterflies differ from those 
of other insects, by being covered with a kind of dust, which 
produces the handsome colors, and which, when touched, 
sticks to the fingers. Under the microscope, it is seen that 
. 
