146 NORTH AMERICAN INSECTS. 
well as those of the raspberry and wild rose, though only 
for a short time; but if they eat the leaves of the grape- 
vine they will die in convulsions within two days. 
These tender caterpillars require to be treated with the 
greatest care. They can not be taken up with the fingers 
and placed upon the leaves, but must be moved with a fine 
paint-brush, or with the soft feather of a partridge or quail. 
Fresh and perfectly dry leaves must be given them twice a 
day, spread out in a sieve, from which they are to be re- 
moved in the same manner—that is, taken up on a feather 
every time they are fed. All the excrements and remnants 
of old leaves must be removed, and the sieve made thorough- 
ly clean, before fresh leaves are placed on it, because any ac- 
cumulation of filth will soon cause them to sicken and die. 
These little beings, as soon as they issue from the egg, 
are able to spin, and may be seen marking their way by a 
fine silk thread. In ten or eleven days after birth they cast 
their skin, and this operation is again repeated three times, 
about as often as every two weeks. When they have cast 
their skin the third time they are usually grown to one and 
a half inches in length, at which period of their lives they 
are subject to diarrhoea and other diseases, caused by damp- 
ness, coarse food, cold or bad air. Besides, they have many 
enemies from which they are in danger, such as mice, moles, 
weasels, lizards, ichneumon, wasps, hornets, dragon-flies, 
and even spiders. The apartments where silk-worms are 
raised must therefore be airy, but dry and clean, and the 
windows protected by gauze to prevent the entrance of nox- 
ious insects. 
After they have cast their skin the fourth time their col- 
or becomes more yellowish, and they will be observed wan- 
dering about uneasily, as if seeking sonie place to alight, 
when some brush should be put near them, upon which 
they may creep and there spin their cocoons. 
These cocoons are of a white or yellow color, and con- 
