LEPIDOPTEEA. 225 



In consequence of this having been remarked, some manufac- 

 turers have attempted to obtain their silk directly from the 

 mulberry leaf ; but they only got a bad floss or refuse silk. This 

 is because the silk is not formed in the mulberry leaf. The 

 organs of insects are laboratories, in which manipulations un- 

 known to man are carried on, manipulations which he has not 

 been able to reproduce. 



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 moult, of the ages of the silkworm, of its maturity? 

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

 of the chrysalis, of the moth, and the eggs. 



The name moult has been given to a sort of crisis during which 

 the renewing of the skin of larvae takes place. When it ap- 

 proaches, the silkworm changes its colour. Its robe, which was 

 white or grey, and opaque, becomes yellow 

 and more transparent. The head swells con- 

 siderably, especially above, and the skin becomes 

 wrinkled (Fig. 202). The worm then fasts, 

 and prepares to cast its skin. It places here Fip . m _ Headof the Silk . 

 and there some silk threads on the sur- worm during moulting. 

 rounding objects. It then slips under these threads, so that 

 during its movements the old skin it abandons is, so to speak, 

 picked up. It then assumes a 

 peculiar position, that repre- 

 sented in Fig. '^03, and remains 

 in it in a state of immobility 

 which has been called sleep _.. 



* Fig. 203. Position of Silkworm while moulting. 



(sommeil). 



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

 oozes forth between the two membranes which separates them, and 

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

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

 splits round the muzzle or snout, on the head and back ; then by dif- 

 ferent movements the animal emerges from its skin, which remains 



