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 f6rced 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 2 on each 

 side of the head, two short antennae, and strong jaws or 

 nippers, placed at the sides of the mouth, so as to open and 

 shut side wise. 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.] 



