130 THE SILK WORM MOTH. 



is unable perfectly to go forward with its labours. 

 Under these circumstances, the worm pierces a hole 

 in, and altogether abandons, the unfinished cocoons, 

 and throws out its remaining threads at random 

 wherever it passes, by which means the silk is wholly 

 lost, and the caterpillar, finding no place wherein to 

 prepare for its change, dies without having effected it. 

 At the end of the third or fourth day, the worm 

 generally completes its task, and has formed its 

 cocoon, which, in size and shape, is like that of a 

 pigeon's egg. It is, however, but seldom that it 

 attains so large a size. The following figure repre- 

 sents the cocoon upwards of two-thirds the usual 

 size, with part of the floss silk removed : 



The operation of spinning, and the emission of so 

 large a quantity of silk, uncompensated by food, 

 causes the worm gradually to contract in bulk; it 

 becomes shrivelled, and the wings of its body 

 approach nearer to each other, and their articulations 

 become more distinctly marked. When the cocoon 

 is completed, the larva rests from its toil, and then 

 throws off its caterpillar garb, and changes into the 

 chrysalis state, and is somewhat like a kidney bean, 



