664 THE POPULAR SCIENCE MONTHLY. 



that live upon other leaves than the mulberry. Among these new im- 

 portations, the two principal ones are the yama-mai worm, which 

 comes from Japan, and feeds upon the leaves of the oak, and the 

 ailanthus worm. The first gives a very beautiful and very fine silk, 

 while that of the second is dull and coarse. But the ailanthus grows 

 very well in unproductive soils, and hence the caterpillar which it 

 nourishes renders an important service. 



But let us return to our mulberry caterpillar, or the silk-worm 

 properly so called. "We left it at the moment when it disappeared 

 from our eyes enveloped in its cocoon. There, in its mysterious re- 

 treat, it becomes torpid once more. It now shortens itself, changes 

 form, and submits to a fifth moulting. But the animal which emerges 

 from the old skin is no longer a caterpillar. It is in some sort a new 

 being ; it is what we call a chrysalis. This chrysalis scarcely reminds 

 us of the silk-worm. The body is entirely swaddled ; we no longer 

 see either head or feet (Fig. 14). The color is changed, and has be- 

 come a golden yellow. Only by certain obscure movements of the 

 posterior part do we know that it is not a dead body. 



This apparent torpor in reality conceals a strange activity in all 

 the organs and all the tissues, which ends in the transformation of the 

 entire being. 



In fifteen or seventeen days, according to the temperature, this 

 work is accomplished, and the last crisis arrives. The skin splits .on 

 the back ; the animal moults for the last time, but the creature that 

 now appears is no longer a caterpillar or a chrysalis : it is a butterfly 

 (Fig. 12). 



Fig. 12. 



Silk-worm Moth (Male). 



Is it needful to explain the details of this wonderful metamorpho- 

 sis ? The body, before almost all alike, presents now three distinct 

 regions : the head, the chest {thorax), the belly [abdomen). Wings, 

 of which there was not the least vestige, are now developed. In com- 

 pensation, the hind-feet have disappeared. The fore-feet persist, but 

 you would not know them, they have become so slender, and a fine 

 down covers all the parts. 



In the interior, the transformation is also complete. The oesopha- 

 gus (throat) is no longer a simple reversed funnel ; it is a narrow, 

 lengthened tube, with an aerial vessel attached, of which the caterpil- 

 lar offers no trace. The stomach is strangely shortened. The intes- 



