MR. NEWPORT ON THE NERVOUS SYSTEM OF THE SPHINX LIGUSTRI. 413 



things were not sufficiently explained, owing partly to want of specimens, and partly 

 to the uncertainty of the period at which the changes take place in different indivi- 

 duals. I determined, therefore, to repeat my observations upon another Lepido- 

 pterous insect, of a different genus, and for this purpose chose the commonest of our 

 British species, the Nettle Butterfly, Papilio urticoe, Linn. Heroldt has accurately 

 noticed the changes in Papilio brassicce, Linn. 



I selected for my observations a large number of the larva of the Nettle Butterfly, 

 and fed them in breeding cages until they suspended themselves preparatory to 

 changing to the pupa state. The moment of throwing off the old skin was carefully 

 watched, and the precise time of its occurrence noted. By these means an adequate 

 number of specimens was collected, and the time the insects had remained in the 

 pupa state accurately known, and the specimens were then dissected at stated pe- 

 riods. The manner in which the insect prepares to undergo its change, and the 

 mode of its occurrence, are known to every naturalist ; I shall therefore confine my- 

 self to the changes of the nervous system, in illustration of what takes place in the 

 Sphinx ligustri. The nervous system of P. urticce, Linn., very closely resembles that 

 of the Sphinx, and has the same number of ganglia. 



Two hours after the insect has suspended itself to undergo its transformation, a 

 considerable change in the arrangement of the nervous system takes place. The cere- 

 bral ganglia are distinct from each other, but are not yet enlarged. When viewed 

 from above, each presents a pear-shaped appearance, the anterior part of the lateral 

 surface being elongated forwards and gives origin to the antennal and optic nerves. 

 At the base of the optic nerves, even at this early period, there is the same appear- 

 ance of dark pigment as in the Sphinx ligustri, from which it is clear that this is 

 deposited in the earliest stages of transformation, both in the Butterfly and Moth. 

 The suboesophageal ganglion is nearly twice its original size, and the crura which 

 connect it to the cerebral ganglia are considerably shorter, as well as the cords that 

 connect the second, third, fourth, and fifth ganglia. The two last are separated only 

 by a short interval, and are slightly enlarged. The fifth, sixth, and seventh ganglia 

 are closer together, the cords between them disposed irregularly, and the longitudinal 

 position of the ganglia altered. The ganglia from the seventh to the eleventh remain 

 as in the active larva. 



By unremittingly watching a number of larva through all their preparatory states 

 for changing, we can easily judge, within a very short period, when the transforma- 

 tion will take place. Just before throwing off the old skin there is much activity 

 throughout the whole insect, and if it be dissected about half an hour [Plate XV. fig. 21.] 

 before this occurs, the nerves for the future wings, and the cerebral, and second, third, 

 fourth, and fifth ganglia are all slightly enlarged, and the first ganglion very consi- 

 derably. The cords which connect them diverge from each other, while those be- 

 tween the fifth, sixth, and seventh ganglia are more folded than in any other part of 

 the body. 



MDCCCXXXIV. 3 H 



