224 Dr. Wallace on 
is seen occasionally to take the edge of the leaf in his jaws at this 
stage, and pull it towards him, evidently to curl it the more. It 
then, as it were, lays another coat of a strong substantial nature 
on the envelope, and fills in with an open network the space be- 
tween the curled edges of the leaf. That is the work of about 
twelve hours, and if we visit the larva early the next morning, we 
find the leaves still more curled, and the network more filled up, so 
that the Jarva can but just be seen at work within. At this stage 
the appearance is very beautiful ; the silk is of a very pure white 
lace-like appearance, and sufficiently open to allow of the bluish- 
green workman to be seen within; soon, however, the covering 
thickens and we lose sight of him, though we hear his incessant 
movements for several days; in about thirty-six hours from 
the beginning the larva is hidden from sight, and the silk begins 
to turn brown, mainly, I think, from an exudation issuing from 
the anus of the larva, for the cocoon is now observed to become 
very soft and wet, especially at the base; this dries in twelve 
hours, leaving the cocoon of a browner colour but much harder ; 
it may now be handled or even gathered without fear of injury to 
its inhabitant. It is this exudation which, valuable as a preser- 
vative to the cocoon, rendering it capable of transportation and 
contributing to its preservation from the attacks of enemies and 
from winter’s cold, yet throws a difficulty in the way of reeling 
the silk. This gum must be got rid of before reeling can be 
done, and one of the difficulties is to find a solvent which will get 
rid of the gum without deteriorating the quality of the silk, and 
at the same time render the manipulation of the cocoon easy for 
reeling. For several days the larva may be heard at work lining 
and relining the interior of the cocoon, which in time becomes 
quite polished and hard, and when dissected the cocoon may be 
taken off in layers or skins, as if skin after skin was added inside 
till the work was done. ‘These skins are sometimes seven in 
number. 
During the process of spinning, we gain an insight into one of 
the purposes of the tubercles. Nature doubtless never constructs 
without a purpose, and often two or three ends are served by one 
construction; during the growth of the larve the spines and 
tubercles keep off the wet and prevent injury from external con- 
tact, and the tubercles likewise secrete a waxy powder which, 
besides keeping the insect dry, serves probably to deter its 
enemies; but during the formation of the cocoon the tubercles 
are seen to be of great use, in keeping the silken threads at some 
little distance from the body of the larva, thereby allowing neces- 
