SILK-WORMS. 
33 
not eat, however, forms part of the weight of the 
leaves which* the cultivator either buys or sells. 
These are strong reasons against the general prac- 
tice of feeding silk-worms on the leaf of the wild 
mulberry. (Chap. XI.) 
The worst leaf that can be given to the silk- 
worm, and which always injures it, is that which 
is covered with what is termed manna , which acci- 
dent arises from the diseased state of the tree, or 
from its superabundant health. I would never 
advise such leaves to be given to the silk-worm, 
except in case of a scarcity, and then even they 
should be washed and dried with great care. 
The blighted, or rust-spotted leaves, do not 
injure the silk-worm. We see numbers of trees 
thus diseased, particularly when they are in damp 
and close situations. The worm will eat this leaf, 
at least will eat the sound part of it, carefully 
avoiding the spots ; where there is no alternative, 
these leaves may be given, but in greater quan- 
tity, that the worm may not fatigue itself in seek- 
ing its necessary proportion of food. These in- 
sects would be injured by eating leaves moist with 
either rain or dew. I shall shew (Chap. VII.) 
how this may be avoided by drying the leaves. 
The greatest care should be taken, whatever may 
be the quality of the leaf, to prevent its being 
heated or fermented, whether just picked or w’hen 
kept, Fermentation alters more or less the nutri- 
