258 
LEPIDOPTERA. 
maturity, are females, they will give forty-five millions of 
caterpillars in the second, and six thousand seven hundred 
and fifty millions in the third generation. These data suffice 
to show that the actual number of these insects, existing at 
any one time, must be far beyond the limits of calculation. 
The greater part of caterpillars subsist on vegetable food, 
and especially on the leaves of plants; hence their injuries 
to vegetation are immense, and are too often forced upon 
our notice. Some devour the solid wood of trees, some live 
only in the pith of plants, and some confine themselves to 
grains and seeds. Certain species attack our woollens and 
furs, thereby doing us much injury; even leather, meat, 
wax, flour, and lard afford nourishment to particular kinds 
of caterpillars. 
Caterpillars vary greatly in form and appearance, but, 
in general, their bodies are more or less cylindrical, and 
composed of twelve rings or segments, with a shelly head, 
and from ten to sixteen legs. The first three pairs of legs 
are covered with a shelly skin, are jointed and tapering, 
and are armed at the end with a little claw ; the other legs 
are thick and fleshy, without joints, but elastic or contractile, 
and are generally surrounded at the extremity by numerous 
minute hooks. There are six very small eyes^ on each 
side of the head, two short antennge, and strong jaws or 
nippers, placed at the sides of the mouth, so as to open and 
shut sidewise. In the middle of the lower lip is a little 
conical tube, from which the insects spin the silken threads 
that are used by them in making their nests and their co¬ 
coons, and in various other purposes of their economy. Two 
long and slender bags, in the interior of their bodies, and 
ending in the spinning tube, contain the matter of the silk. 
This is a sticky fluid, and it flows from the spinner in a 
fine stream, which hardens into a thread so soon as it comes 
[2 Though Dr. Harris mentions the “eyes” of caterpillars, yet be it under¬ 
stood, he does not assert that they see. It is very doubtful whether they have the 
faculty of vision. — Morkis.] 
