PUPA CASKS. 55 
(lergroiind, and work out a sort of cell, 
where tbeir metaphorphosis is effected. 
Again, those kinds which spin, have 
different ways of doing it. 
Lucy, Do you mean like the wonder- 
ful oak caterpillars, that spin their brown 
tents to live in by hundreds ? 
Mother, They, you know, spin those 
tents to live in while they remain cater- 
pillars ; but I allude to certain species 
that spin round themselves the case in 
which they are to make their change. 
Lucy, That is like the silk worms, of 
which I have heard Fanny speak. 
Mother, Yes, and no other kind has 
yet been found worth the trouble of cul- 
tivating, for the sake of the materials of 
which those cases are composed, though 
a very large proportion of the caterpillars 
of both moths and sphinges have the 
same habits. Their cases vary in form and 
colour, and indeed in the disposition and 
texture of the silk ; some are oval, rough, 
and of a pale brown or yellow colour; 
while others are egg shaped, full at one 
