2 22 THE INSECT WORLD. 



o-lands. At this period the animal eats much ; and it is certain that 

 the substance to be converted is furnished by the leaf of the tree on 

 which the insect feeds. 



In consequence of this having been remarked, some manufacturers 

 have attempted to obtain their silk directly from the mulberry leaf; 

 but they only get a bad floss or refuse silk. This is because the silk 

 is not formed in the mulberry leaf. The. organs of insects are labora- 

 tories, in which manipulations unknown to man are carried on, 

 manipulations which he has not been able to imitate. 



After this rapid glance at the fundamental parts of the organism 

 of the silkworm, we will occupy ourselves with the natural history, 

 properly so called, of this insect, and with its rearing, carried on with 

 a view to the production of silk. 



As belonging to the first part of this programme, we have to speak 

 of the moiUt^ of the ages of the silkworm, of its maturity, of its 



■ 



Fig. 202. _ Fig. 203. 



Head of the Silkworm during moulting. Position of Silkworm while moulting. 



mounting or ascending season, of the formation of the cocoon, of thej 

 chrysalis, of the moth, and the eggs. 



The name moult has been given to a sort of crisis during whicli t^ 

 the renewing of the skin of larvae takes place. When it approache 

 the silkworm changes its colour. Its robe, which was white or gre 

 and opaque, becomes yellow and somewhat transparent. The h( 

 swells considerably, especially above, and the skin becomes wrinl 

 (Fig. 202). The worm then fasts, and prepares to cast its skin, 

 places here and there some silk threads on the surrounding objecf 

 It then slips under these threads, so that during its movements 

 old skin which it will abandon is, so to speak, gathered up. It the 

 assumes a peculiar position, that represented in Fig. 203, and remf 

 in it in a state of immobility which has been called sleep {sommeil).^ 



During this sleep the new skin is formed under the old. A liqi 

 oozes forth between the two membranes which separates them, a: , 

 allows the silkworm to leave its old skin. To effect this, the won 

 begins by raising its head, and by making contortions. The old ski 

 splits round the muzzle, or snout, on the head and back ; then \ 



