224 ^^^ INSECT WORLD. 



remarked a physiological fact to which has been given the name of 

 freze. When the silkworm has just moulted it eats Httle, but the 

 time very soon arrives when it does so with extraordinary avidity. 

 It is indeed insatiable. T\\^ freze of the last age is called the grande 

 freze. It takes place about the seventh day. During this day worms, 



ic, 



^ W 



)d 



Fig. 208. — Fifth age. 



the produce of thirty grammes"' of eggs, consume in weight as much 

 as four horses, and the noise which their httle jaws make resembles: 

 that of a very heavy shower of rain. It is at the end of this stage 

 that the insect prepares the shelter in which is to be brought about 

 its metamorphosis into a chrysalis. 



A little while before this it ceases to eat, turns yellow, and 

 becomes as transparent as a grape. It is now said to have reached 

 its maturity. Up to this moment the worm had never tried to leave 

 its litter. It lived a sedentary life, and never thought of wandering 

 away from its food. Now it is seized with an imperious desire for 

 changing its quarters. It gets up, it roams about, and moves its 

 head in all directions to find some place to cling on to. It walks 

 over everything within its reach, particularly over those obstacles 

 which are placed vertically. It aspires, not to descend, like the 

 heroes of classic tragedy, but to rise. It is for this reason that this 

 period of the silkworm's life has received the name of the mounting 

 or ascending season. It now looks for a convenient place in which to 

 estabhsh its cocoon. Every one has remarked how the animal sets 

 to work to accomplish its task. It begins by throwing from different 

 sides threads destined for fixing the cocoon ; this is what we cal] 

 refuse silk. The proper space having been circumscribed by this 

 means, the worm begins to unwind its thread — a continuous thread 

 of about a thousand metres long. 



It has been calculated, let us say by the way, that forty thousanc 

 cocoons would sufiice to surround the earth at the equator with on( 

 thread of silk. Folded on itself almost hke a horse-shoe, its bacl< 



* One gramme = 15-4325 gr. troy. 



