50 NATURAL HISTORY. [CH. III. 



composed of materials furnished by the caterpillar 

 itself, being either entirely of silk, or of silk min- 

 gled with the hairs of the caterpillar ; and his thir- 

 teenth memoir, comprising cocoons of an irregular 

 form, in which other matters besides silk are em- 

 ployed. As these memoirs would occupy at least 

 one hundred and fifty of our pages, we can give but 

 an imperfect idea of the various objects treated 

 upon. In the subsequent pages of this chapter we 

 have, however, endeavoured to introduce an account 

 of the chief peculiarities of structure, with some 

 additional information and remarks. 



Among those insects which form their cocoons 

 of pure silk, the silkworm stands far pre-eminent ; 

 for, as Reaumur observes, if the luxury of silk were 

 taken away, where could wool sufficient to supply 

 its place be found 1 The poor, he adds, would be 

 obliged to go unclad, unless, indeed, he should dis- 

 cover some method of employing the silken co- 

 coons of other insects, which are sufficiently com- 

 mon, and equally prolific, and which seem to be well 

 adapted for such an experiment : indeed, Reaumur 

 endeavoured to rear a tubercled species of caterpil- 

 lar, found in the pear, for that purpose, but he did 

 not succeed, except in one instance, in which the co- 

 coon weighed as much as three of those of the silk- 

 worm. 



Some species of caterpillars being probably un- 

 provided with a sufficient supply of silk, content 

 themselves with spinning a cocoon of so flimsy a 

 construction as to resemble network, allowing the 

 chrysalis to be perceived without difficulty, and 

 seeming formed merely as a support rather than as 

 a defence to the enclosed animal. Of this descrip- 

 tion is one noticed by Messrs. Kirby and Spence, 

 somewhat resembling an air balloon, the meshes of 

 which are large and perfectly square. The pupa 

 hangs in the centre, fixed by some few slight threads, 

 which diverge from it to all parts of the cocoon, so 



