OF THE SPHINX LIGUSTRI. 
393 
hausted as to be unable to rid itself of the exuviae, and complete its transforma¬ 
tion, owing- to its having been prevented from remaining at rest during the 
proper period, the change in its nervous system is never so much advanced 
as in those which have transformed without interruption ; nor does it make 
any further progress even in seven days, while the insect itself generally 
perishes in less than a fortnight. 
After the insect has remained for about five weeks in the pupa state, scarcely 
any further change occurs in its nervous system until the following spring. 
This period of repose, during which the insect remains nearly torpid in its cell 
in the earth, continues for at least twenty-three or twenty-four weeks, and ex¬ 
tends in general from the middle of October to the beginning of the following 
March, when, if the season be temperate, the change again advances. If the 
pupa be examined at any time during this interval, scarcely any alteration is 
observed in its nervous system, except an enlargement of the anterior lateral 
ganglia. 
In the beginning or middle of March, when the pupa is becoming more 
lively, a change in the nervous system is evidently in progress. The cerebral 
lobes, [PI. XIII. fig. 1.&2. (a, a),] when viewed from above, are distinct 
from each other, are increased in size, and are of an irregular spherical figure. 
The ganglion called the recurrent, [fig. 2. (e),] rests immediately above a 
semi-cartilaginous arch, that forms the upper part of the mouth, while its 
nerve passes backward as before, distributing its filaments to the oesophagus, 
and anterior part of the dorsal vessel. The nerves to the antennae are still in 
the same state as before, but a small branch [fig. 2. (d, f)~\ may now be 
observed coming from their base, and directed downwards towards the mouth, 
and apparently connecting itself with the filaments from the nerves which be¬ 
longed to the mandibles, and also to one from the anterior lateral ganglia, 
[fig. 2. (g).] The optic nerves are extending, and are greatly enlarged at 
their base, [fig. (b, b),] but there is no enlargement of the patch of dark pig¬ 
ment, [fig. 2. (b, c).] The nervous circle still exists around the anterior of the 
oesophagus, [fig. 2. (f),] and the anterior lateral ganglia are greatly increased 
in size, and still originate in the same manner as in the larva. But the nerves 
they distribute, and the connexions they form with other nerves, are more 
easily detected at this than at an earlier period. The first one, the lunated 
