226 INSECTS INJURIOUS TO VEGETATION. 



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 antennae, 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 cocoons, 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 to the air. Some caterpillars make but very little silk ; 

 others, such as the silk-worm and the apple-tree caterpillar, 

 produce it in great abundance. 



Some caterpiflars herd togetheB in great numbers, and pass 

 the early period of their existence in society; and of these 

 there are species which unite in their labors, and construct 

 tents serving as a common habitation in which they live, or to 

 which they retire occasionally for shelter. Others pass their 

 lives in solitude, either exposed to the light and air, or shel- 

 tered in leaves folded over their bodies, or form for themselves 

 silken sheaths, which are either fixed or portable. Some make 

 their abodes in the stems of plants, or mine in the pulpy sub- 

 stance of leaves; and others conceal themselves in the ground, 

 from which they issue only when in search of food. 



Caterpillars usually change their skins about four times 

 before they come to their growth. At length they leave off" 

 eating entirely, and prepare for their first transformation. 

 Most of them, at this period, spin around their bodies a sort 



