64 METAMORPHOSES OF MAN 



portion, and the large intestine to the loaded part. 

 At the same period the salivary glands and biliary 

 coeca are reduced by about two-thirds, and the silk- 

 secreting organs appear as two very slender threads. 



During the entire winter — that is to say, for five or 

 six months of the year — these operations are sus- 

 pended; but they are recommenced in fine weather, 

 and continued till the insect is fully formed. In a 

 short time the silk-forming canals have entirely dis- 

 appeared ; hardly a trace of the salivary glands is to 

 be found; and the stomach, though preserving its 

 former shape, has decreased in size ; but to compen- 

 sate for this, it has developed a new cavity called a 

 crop, which is destined to assist in sucking up the 

 juices of the flowers and retaining them till required 

 by the insect. Moreover, the two intestinal regions 

 have become more distinct, and the large intestine 

 has developed an accessory pouch, not a trace of 

 which existed hitherto. 



We come now to the nervous system. In Annulosa 

 generally, and hence in insects in every condition, 

 this system is composed of two distinct portions. The 

 brain is placed in the head just above the oesophagus. 

 The other nervous masses, or ganglia, are situate 

 below the digestive tube, where they constitute a 

 ganglionic chain. The brain is united to the first 

 ganglion, this to the second, and so on, by a series of 

 nervous filaments, technically termed commissures. In 

 each ring of the caterpillar's body there is a distinct 

 ganglion; consequently there are in all twelve of 

 these structures, equally distant from each other, with 

 the exception of the two first, which are more closely 

 approximated than the rest. The brain itself is very 



