METAMORPHOSES OF INSECTS. SILKWORM. 107 



thin pellicle, which lies over the external organs, follows all 

 their inequalities of surface, and causes the insects to appear as 

 if closely wrapped in bandages. 



683. Before undergoing this change, the Larva often pre- 

 pares a defence for itself ; and shuts itself up in a case, which it 

 makes with silk, secreted by peculiar glands, and drawn out by 

 means of a spinneret, a small tube attached to the lower lip. In 

 other instances, it suspends itself by means of threads, or conceals 

 itself in some hollow. It is, however, whilst the insect is in this 

 state of apparent repose, that active operations are going on with- 

 in the body, of which the result is the complete development of 

 the entire organisation. Its interior parts become soft, and by 

 degrees assume the shape that they will preserve ; the different 

 organs, with which the adult animal ought to be provided, are 

 developed under the envelope which conceals them ; and when 

 this evolution is finished, it frees itself from this species of mask, 

 spreads its wings, which are not long in acquiring firmness, and 

 becomes a perfect insect or Imago. 



684. As an example of this complete metamorphosis, we can- 

 not make a better selection, than by taking the Bombyx Mori ; 



for this insect in 

 its larva state pos- 

 sesses for us an 

 immense interest ; 

 it is the silkworm, 

 the rearing of 

 which contributes 

 so powerfully to 

 the agricultural 

 prosperity of the 

 southern countries 

 of Europe, and the 



FIG. ^.-SILKWORM, product of which 



gives origin to so much industry and wealth. This insect came 

 originally from the northern provinces of China, and was not 

 introduced into Europe until the sixth century. The Greek 

 Missionaries brought some of its eggs to Constantinople in the 



