LEPIDOPTERA. 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 get 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 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 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 larve takes place. When it ap- 
proaches, the silkworm changes its colour. Its robe, which was 
white or grey, and opaque, becomes yellow 
and somewhat 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 gis, 909 Head of the Silk. 
and) there some silk threads on the sur-  “™" Cs moulung. “ 
rounding objects. It then slips under these threads, so that during 
its movements the old skin which it will abandon is, so to speak, 
gathered up. It then assumes a 
peculiar position, that repre- Pri Cy 
sented in Fig. 203, and remains go! 
in it in a state of immobility 
which has been called sleep 
(sommeit). 
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 
different movements the animal emerges from its skin, which 
Q 





Fig. 203.—Position of Silkworm while moulting 
