creatures weave the cases in which they pass their 

 aurelia.state. Some are made of silk, mixed with their 

 own hair, with pieces of bark, leaves, wood, or 

 paper. 



There is one sort that build in wood, and gives its 

 case a hardness greater than that of the wood itself. 

 This is the caterpillar of the willow, which is one of 

 those that eat their exuvias. He has sharp teeth, where- 

 with he cuts the wood into a number of small frag* 

 ments. These he unites together into a case, by means 

 of a peculiar silk, which is a viscous juice that hardens 

 as it dries. In order to make this silk enter into the 

 very substance of the fragments, he moistens every 

 one of them, by holding them successively in his 

 mouth for a considerable time. In this firm case he 

 is afterward to be included till he becomes a butterfly. 

 But how shall a creature of this helpless kind, which 

 has neither legs to dig, nor teeth to gnaw, get out of 

 so firm and strong a lodgment as that wherein it is 

 hatched ? Nature has provided for this also. As soo;i 

 as it is hatched, it discharges a liqu >r which dissolves 

 the viscous matter that holds the case togethe^ so that 

 the fragments fall in pieces of themselves ; and accord, 

 ingly, near its mouth, there is always found a bLadder 

 of the size of a small pea, full of this liquor. 



Some caterpillars spin all the way they walk, a thread 

 of silk which marks their journey. Now what end 

 does this serve? A little observation will shew. Trace 

 one of them till he chances to fall, and you will sue 

 the use of this thread. Bein^ fastened to the leaves 

 and twigs, it stops the creature's fail. Nor is this all. 

 It can also by means of this thread re-ascend to the 

 place from whence it fell ; and when it is sate g )t up 

 again, it continues its motion as before. 



Another curious artifice is that by which the same 

 species of caterpillars make themselves cases of leaves 

 before they change into aurelia. The nicest ha:ds 

 could not roll these up so regularly, as they do with- 

 out hands or any thing like them. They perform it 

 thus ; the caterpillar places itself on the upper side of 

 E2 



