OF THE SPHINX LIGUSTRI. 
385 
there are two very distinct ganglia, with intervening cords, which afterwards 
unite to form the terminal ganglion of the perfect insect. 
In describing the nerves distributed from these ganglia, it may be well to 
consider them as belonging to the head, the thorax and abdomen. In the first 
there are the cerebral lobes and first ganglion, which are found in the head in 
every period of the insect’s existence, but undergo a modification of form, 
are increased in diameter, and furnish nerves to the organs of sense and man- 
ducation. The second division comprehends the ganglia which furnish nerves 
to the true limbs, or organs of motion. These ganglia are contained in the 
second, third, fourth and fifth segments of the larva, which correspond to the 
collar and trunk of the pupa and perfect insect. The third or abdominal 
division comprises the ganglia in the eight last segments in the larva, and 
the corresponding ones in the pupa and perfect state. The cords in this divi¬ 
sion are much shortened, and the number of the ganglia diminished, during 
the change of the insect from the larva to the perfect state. 
Nerves of the Head .—When viewed from above, the cerebral lobes are pretty 
uniform in appearance, and are clearly distinguished from each other by a de¬ 
pression between them. This is more apparent on the anterior than the pos¬ 
terior surface, and arises from the lateral part of each lobe being carried a 
little forwards, so that the two lie across the oesophagus in a curved or semi¬ 
lunar direction. From the anterior and lower part of each lobe originate four 
remarkable nerves. Two of these [Plate XII. fig. 2. ( d , d, d, rf)] are distributed 
towards the front of the head, near the flexor muscles of the mandibles; a 
third passes a little forwards, descends, and, uniting with its fellow from the 
opposite lobe, forms a circle [fig. 2. (f)] round the oesophagus, to the under 
surface of which it distributes a few filaments; while the fourth, which origi¬ 
nates rather higher up than the others, forms what has been called by Lyonnet 
the recurrent ganglion and nerve, [PI. XII. fig. 2. (e); PI. XIII. fig. 2. (e).] 
From its origin, this nerve is directed forwards and downwards, along the side 
of the oesophagus, or rather posterior part of the mouth, but gradually altering 
its course inclines upwards and inwards, and then a little backwards, until, 
by meeting its fellow of the opposite side above the roof of the mouth, the 
two by their union form a semilunar ganglion [PI. XII. and XIII. fig. 2. (e)] 
immediately below the bifurcated portion and distribution of the dorsal vessel. 
