In this paper it is proposed to describe the development and arrangement of the nerves, and the changes which they undergo, in the Sphinx Ligustri , Linn., during the last stage of the larva, and the earlier stages of the pupa state. The labours of that industrious naturalist Heroldt have already shown us, to a certain extent, in what manner similar changes occur in the Papilio Brassincæ Linn.; and therefore the author of the present essay would not have ventured to trespass upon the attention of the Royal Society, were it not that these changes are capable of more minute explanation than those which take place with such rapidity in the P. brassicæ . But the Sphinx ligustri , Linn., remaining as it does for several months in an apparently torpid condition, between its larva and perfect state, allows us an opportunity of more deliberately observing in what manner the changes are effected; while the superior bulk of the insect enables us to trace them with greater precision.